Cocoon-like trace fossils from the lacustrine-palustrine BembridgeLimestone Formation (Late Eocene), Southern England

Nicholas Edwards*, Edmund A. Jarzembowski",Thomas Paint and Brian Daley*

EDWARDS, N., JARZEMBOWSKI, E. A., PAIN, T. & DALEY, B. 1997. Cocoon-like trace fossils fromthe lacustrine-palustrine Bembridge Limestone Formation (Late Eocene), Southern England.Proceedings of the Geologists' Association, 109, 25-32. In exposures of the Late Eocene BembridgeLimestone Formation at the west end of the Isle of Wight, calcareous ovoid-cylindrical trace fossils,ranging in length from 1to over 47 mm long, but commonly 30 mm long and 15 mm in diameter, occursparingly distributed in freshwater to pedogenically-modified limestones yielding calcitic casts offreshwater snails and land snails. Although specimens of the trace fossils having both ends entire areusually preserved as calcitic to calcite internal casts, the occurrence of rare hollow specimens lined bydrusy calcite is evidence that they were chambers within the sediment. The majority of specimens wereruptured sub-terminally at one end before fossilization, probably by the escaping organism. Suchspecimens are partly to entirely filled by intrac1astic lime mudstone. Rare specimens are attached to ashort burrow-fill composed of similar lime mudstone and about the same diameter as the chamber. Mostchambers have a surficial film of chalky micrite or microspar, with or without a cemented surficialmicritic skin. In some specimens the micritic skin protects a surface ornament of lobate and compositelobate-linear ridges 0.5 mm wide and up to 5 mm long. When weathered-out in relief, these impart awrinkle-like or fibrous surface texture, which can have a distinct helical trend. Whereas hitherto thechambers have been interpreted as tropical land snails' eggs, they differ from the latter in shape, surfacetexture, mode of rupture and mode of occurrence. The chambers also lack an egg-shell microstructureand cannot be reptile eggs. Although some analogous foreign specimens have been interpreted as simplehymenopteran brood chambers, fossil and Recent examples of these have a distinct terminal cap or seal,lacking in the Bembridge Limestone specimens. Instead, they may have been made by other kinds ofinsect for pupation, or by an unknown organism for aestivation or hibernation.

*Department of Geology, University of Portsmouth, Portsmouth POI 3QL."Maidstone Museum & Art Gallery, St Faith's Street, Maidstone, Kent MEl4 lLH and PostgraduateResearch Institute for Sedimentology, The University, Reading RG6 2AB.*131 Wakeley Road, Rainham, Kent ME8 8NP.

1. INTRODUCTION

The Late Eocene Bembridge Limestone Formation,preserved only in the Isle of Wight, southern England, is thethickest and most extensive of a number of pale brown tocream-coloured limestones in the mainly fine-grainedclastic Late Eocene-Early Oligocene Solent Group. Likemost of the other limestones, it contains abundant shells orinternal casts of freshwater snails and since the earlynineteenth century has been regarded as lacustrine.Armenteros, Daley & Garcia (1997), however, whilerecognizing a 'lacustrine' facies, dominant at the easternend of the island, have also recognized a 'palustrine' facies,dominant at the western end of the island. The lattercomprises marginal-lacustrine limestones modified bysubaerial exposure and pedogenesis, includingcalcretization. A lake-margin situation is supported by theoccurrence of a large assemblage of land snails (Pain &Preece, 1968; Preece, 1976, 1982), together with pondsnails, at the western localities.

The present paper concerns ovoid-cylindrical calcareous

Proceedings of the Geologists' Association, 109,25-32.

bodies about the size of small birds' eggs, here interpretedas trace fossils. They are commonly associated with calciticcasts of land snails and pond snails in the palustrine facies,and are readily collected from talus at the Headon Hilllocality (see below). Exceptionally well preserved speci­mens display a helical-linear surface texture.

Pain & Preece (1968) accepted a long-held opinion thatthe trace fossils are the eggs of tropical land snails of thegenus Filholia, redescribed by Nordsieck (1985) as aclausiliid, present in the Bembridge Limestone at thewestern localities. However, identification of the tracefossils as land snails' eggs has never been criticallyexamined. It was first tentatively proposed by Edwards(1852: 121-122) and elaborated upon by Gardner (1885:243-244), who provided the only detailed publisheddescription. While observing that the trace fossils couldhave passed through the aperture of mature adult specimensof these snails, the latter author nevertheless remarked thatRecent tropical land snails' eggs are ovoid and smooth­shelled, not ovoid-cylindrical and rough textured. Asdiscussed below, these and other differences, confirmed by

0016-7878/98 $10·00 © 1998 Geologists' Association

26 N. EDWARDS E T AL .

2. OCCURRENCE

3. DESCRIPTION

Morphology

Specimens commonly found are ovoid-cylindrical, slightlyto moderately inflated. Those examined are 16 mm to over47 rnm long and 8 mm to 25 mm in diameter, but most areapproximately 30 mm long and 15 mrn in diameter (Fig. 2).The following description is based on rare, exceptionallywell preserved specimens in the latter size class, showingwell-defined surface textures. The three specimens figuredare now in the Palaeontological Collections of the NaturalHistory Museum, London, catalogue numbers PX TF18-PX TF 20. Preservation of most other specimens of allsize classes is poor and surface textures are either difficultto study or absent.

Some specimens have a brown secondarily cementedmicrite skin 0.02- 0.03 mm thick (Fig. 3), but mostcompri se only the underlying film of whitish, grey orbrownish chalky micrite (in many specimens patchily toentirely microsparitized) 0.10-0.15 mm (rarely I mm)thick. In entire specimens, with both ends rounded (Fig. 4a),this is distinct from or (if strongly microsparitized) gradesinwards to drusy calcite approximately 0.20 mm thick.Entire specimens can be hollow, but more commonly theyhave a core of translucent blocky calcite. No organicremains were present in entire specimens sectioned byGardner (1885) and during the present study.

Approximately 90% of specimens are intraclastic limemudstone and calcite internal casts. In these, one end isirregularly ruptured outwards subterminally to terminally, atan angle of up to 45° to the long axis (Fig. 4b) . In suchspecimens of the size class described here, the rupture isapproximately 1.0 cm wide. Measurements on the uppersurface of three partial, geopetal lime mudstone internal fillsof ruptured specimens showed that, when ill situ, onespecimen was horizontal and the other two were tilted uptowards the disrupted end at 10 to 20° from the horizontal.

In two calcitic and intraclastic lime mudstone internalcasts and one of the geopetally-filled specimens, one end isconcealed by a sub-terminal to terminal cylinder ofmoderately well cemented intraclastic lime mudstone,confluent to slightly narrower (necked) at the junction withthe ovoid-cylindrical part of the trace fossil. In one of thespecimens (Fig. 4c), the cylinder is 15 mm long and 12 mmin diameter, slightly curved and widening abruptly at thefree end to 13 mm in diameter. In the field, cylinders breakoff readily, leaving a stump 2 to 5 mm long and 10 to 12 mmin diameter attached to the ovoid-cylindrical trace fossil.When well-preserved, they bear approximately axis-parallellobate ridges (see below). Except in one specimen, these donot extend across the junction with the ovoid-cylindricalpart of the trace fossil.

N

Prospect Quarry r

1 ° 30 ' W

Cliff End

Headen Hill

Specimens described in this paper are from three localities(Fig. I).

I. North face of Headon Hill [SZ 317 863]. The tracefossils are common in talus deposits below the outcrop,mainly as lime mudstone internal casts detached fromthe matrix. Two found in situ were in a nodular course ofpalacokarsted, tufaceous to well-lithified limestone (bed3 of Daley & Edwards, 1990, fig. II ). A reworkedunlithified mudstone internal cast was found at the baseof a palaeochannel-fill (bed 8).

2. Prospect Quarry [SZ 385 866]. The trace fossils occurnear the top of a thick, fossiliferous, well-lithified,palaeokarsted limestone (bed 3 of Daley & Edwards,1990, fig. 8), regarded by Armenteros, Recio & Daley(1992) as having been calcretized. Reworked specimensoccur in breccio-conglomerates in and above the mainproductive bed.

3. Cliff End [SZ 333 892]. In a now overgrown exposure,the trace fossils occur about 0.3 m below the top of thesection, in a friable but patchily Iithified white chalkylimestone.

examination of the eggs of several Recent tropical land snailtaxa, now militate against identification of the trace fossilsas tropical land snails' eggs.

Although the primary purpose of this paper is to correctthe current misidentification, it is hoped that it willstimulate discussion and furth er research, perhapsascertaining the true origin of these trace fossils.

At all these localities, the trace fossils are sparsely andrandomly distributed and, except for penecontempor­aneously reworked specimens, are not in close contact withone another.

Fig. 1. Location of Bembridge Limestone exposures yielding tracefossils described in thispaper.

oI

5 kmI Surface textures

To the naked eye, most specimens are either smooth orrough-textured, depending on the nature of the surface, itsdegree of cementation and whether the specimen is fresh

TRACE FOSSILS FROM THE LATE EOCENE, S ENGLAND 27

+

o+ +

20EE~...<llE.~-0

f- 10 +*+** *+

o

o

+t* + +

+

o

+

n = 49

o 10I

20I

3~ 40I

length mm

Fig. 2. Length versus diameter cross-plot of entire chambers and Recent tropical land snails' eggs: + = one chamber; * = more than onechamber; 0 = land snails' eggs.

0.5 mm

Fig. 3. Line-drawings of petrographic thin sections of outer layersof a chamber: (A) showing transverse section of a lobe; (B)showing longitudinal section of a lobe. a =cemented micrite skin,b = microspar film, c = drusy calcite (black lines and dots areinclusions of unidentified composition) .

or weathered. Surface textures are best preserved inmoderately well weathered specimens in which the surfacefilm is chalky and protected by a cemented micritic skin.Under a binocular microscope, the circumferential to helicaltexture of raised lineations is seen to comprise lobes and/or

composite lobate ridges, with a relief of up to 0.2 mm.These features have their maximum expression on the outersurface of the surface film and are less well-developed onthe outer surface of the drusy calcite layer (Fig. 3a) .

Lobes (Figs 4a & 5a) are semicircular in cross-section,0.5 mm wide and 2 to 5 mm long, open to the interior of thetrace fossil (Fig. 3). The distal end is blunt to rounded andcan be slightly projecting at its extremity. The proximal endnarrows and grades into the general surface, or is concealedbeneath an overlapping lobe. In one specimen the widely­spaced lobes (6 or 7 per 6 mm width) are in two sets, in eachof which the rounded distal ends face diagonally away fromthe nearest end of the trace fossil. The two opposing setsmeet at a wavy circumferential zone, which is either abrupt,or is marked by lobes and blobs with indeterminate facingdirections. In several specimens, damage to the micritic skincoating the entire specimen allows preferential weatheringof the uncemented cores of lobes and lobate ridges, toproduce a secondary tubular structure.

Lobate ridges (Figs 4b & 5b) are up to 5 mm long andapproximately 0.7 mm wide, parallel to one another orcrossing over underlying lobate ridges at low angles. At theends of specimens, lobate ridges either form a roughly spiralpattern, or tend to meet at acute angles (Fig. 6a).

Mudstone cylinders display simple lobate ridges 0.5 toI mm wide (Fig. 4c). These are aligned approximatelyparallel to the long axis, are straight to gently curving,parallel to subparallel and closely-spaced (three or four per4mm width).

A few specimens additionally display randomly arrangedfine tubules (Figs 6b & c), 0.1 mm diameter and up to I mmlong, straight or curved and occasionally U'-shaped inhorizontal plan. They can bifurcate at angles of up to 40°

A

ab

c

28

(a)

N. EDWARDS ET AL.

(b)

Fig. 4. Photos of trace fossil morphologies and surface textures: (a) chamber displaying a surface texture of lobes, with both ends rounded,PX TF 18; (b) chamber displaying a surface texture of lobate ridges, with one end disrupted outwards by the escaping constructororganism, PX TF 19; (c) chamber with one end concealed by a micritic cylinder displaying axis-parallel lobate ridges, interpreted as thecast of the burrow made by the constructor organism, PX TF 20. Specimens from Prospect Quarry, Isle of Wight. PX TF 18-20 are NaturalHistory Museum (NHM) catalogue numbers. Scale bars = 5 mm.

and occur at all angles to lobate ridges, passing across themand sometimes appearing to branch off them at acute toright angles (Fig. 6b). Apparently disconnected trains oftubules seem to be formed by the topographically high partsof single undulose tubules (Fig. 6c). In one specimen,tubules form interwoven mat-like patches.

Remarks

The symmetrical and consistent form of entire specimens,the approximately linear distribution of dimensions of thevarious size ranges (Fig. 2) and the occurrence of hollowspecimens is interpreted here as evidence that these objectsare trace fossils, originally chambers, probably constructedin consolidated sediment. The occurrence of penecontem­poraneously reworked specimens is evidence for their earlyconsolidation. The common occurrence of specimensruptured outwards at one end is evidence that this was thepreferred method by which the organism escaped from thechamber. Location of lime mudstone cylinders only at theends of the three chambers attached to them is interpreted as

evidence that they are burrow-fills. Their apparent raritysuggests that they were made during construction of thechamber in consolidated sediment and usually damaged bythe organism when escaping, possibly because the sedimenthad been made less competent due to wetting.

The morphology of these trace fossils therefore isinterpreted as evidence that the chamber and the cylinderwere integral parts of a burrow system. Because entirespecimens of the chambers have symmetrically roundedends and lack a distinct terminal seal or cap, it seems likelythat during excavation of the chamber the burrow was back­filled by the constructor from within, rather than the spoilhaving been removed via the burrow and the chambersealed from outside. This interpretation implies that theorganism was preparing for pupation, hibernation oraestivation.

After the organism had escaped, the chamber becamepartially to entirely filled by carbonate mud mixed withsmall lime mud clasts. In one sectioned specimen, the mudwas introduced episodically and clasts were formed in situby dessication of mud layers. This agrees with the sedi-

TRAC E FOSS ILS F R O M THE LAT E EOCE NE, S E N G LA N D 29

(a)

(a)

Fig . 6. Surface textures displayed by chambers: (a) lobate ridges atone end of a chamber; (b) tubules associated with lobate ridges; (e)tubules and tubule trains. Viewed with long axis of chambers heldvertically in (a) and (b), obliquely down to the left in (e).

0.5 mm

if'

~ : .',.'.}'..... "$ #r1 If(e)

~•....•.,,)~

\\ . .; . ~ . ~

. '.:..'~ . ' . . :. .: ." '. ": 0', . . ~ ". : : •• • • •

0.5 mm

(b)

(b) 1 mm

Fig. 5. Surface textures displayed by chamber s: (a) lobes; (b)lobate ridges. Viewed with long axis of chambers held vertically.

mentological evidence for a semi-terrestrial environmentwith ephemeral water cover.

There seem to be two possible interpretations of thesurface lobes and lobate ridges. Although mutuallyincompatible, each has its merits.

I. Their symmetrical arrangement and bipolarity on thechambers suggests that they are tool marks made duringchamber and indicating a rotational mode of excavation,perhaps involving the use of mandibles. This wouldexplain why they are mainly open to the interior, but

does not satisfy the observation that distal ends tend tobe free-standing, and that lobes and lobate ridges tend tooverlap one another.

2. Their morphology and overlapping habit suggests thatthey are infaunal feeding traces, not associated withexcavation of the chamber. Because they are helicallyarranged and open to the interior they would have tohave been produced by systematic, serial forays fromwithin the cavity, possibly to exploit organic matter usedto consolidate or waterproof the chamber wall, or amicrotlora involved in its decay. The inwardly-openform and helical arrangement might thus be evidence forthe existence of an internal lining or cocoon with adistinct helical fabric, which acted as a template. Thisinterpretation does not explain the observed bipolarity ofthese surface features.

30 N. EDWARDS ET AL.

The fine cylindrical tubules can be interpreted moreconfidently as later infaunal feeding traces. They recordapproximately horizontal, random burrowing within andabove the chalky film surrounding the chamber.

4. DISCUSSION OF PUBLISHEDINTERPRETATIONS

As noted in the Introduction, the morphology and mode ofoccurrence of the chambers precludes their interpretation astropical land snails' eggs. Recent examples collected by oneof us (TP) are shorter relative to their diameter than theBembridge Limestone chambers (Fig. 2), are calcareous,smooth, whitish, porous, translucent and slightly glossywhen unweathered. They are also very brittle and it seemsunlikely that the young would hatch by bursting open oneend. There is also no record of land snails' eggs being laidin mud or at the end of burrows. Recent achatinids' eggs, forexample, are either retained within the body (Hirsch &Harris, 1989), or laid in leaf litter, or in rolled-up leaves stillon the tree.

Similar objections can be made to the interpretation, byKuntz (1983), of analogous West European Middle Eoceneovoid-cylindrical trace fossils as the eggs of snakes andother reptiles. Specimens from the author's locality werecited by Hirsch (1994: 280-281) as 'pseudo-eggs', a classincluding nodules and insect cocoons. These lack thecharacteristic microstructure of eggshell, described byHirsch (1994, 1996). It is also significant that Kuntz (1983)did not state that his trace fossils occur in clutches, unlikereptile eggs.

Edwards (1852: 121-122) noted that the chambers hadbeen interpreted, presumably informally, as insect cocoons.Similar trace fossils from the Middle Eocene palustrine­lacustrine Creechbarrow Limestone, Dorset, in the middlesize range of Bembridge Limestone specimens, wereinterpreted by Hooker (1986: 435, p l. 35, figs 4a & b) asinsect burrows. Many Lepidoptera, Coleoptera, Diptera andsome Neuroptera make simple burrows ending in chambers,either for laying their eggs, e.g. the scarabid beetlesCanthon spp. (Ratcliffe & Fagerstrom, 1980) and thechafers Bledius spp., Heterocerus spp. and Dyschirius spp.(Larsen, 1936, figs 41 & 46-48), or for pupation. However,none of those figured in the literature, including sub-fossilcalcified cocoons of soil-burrowing insects figured by Lea(1925), resemble the Bembridge Limestone chambers.

A suggestion by Preece (1980: 177), that the helicallinear surface texture displayed by specimens from theCreechbarrow Limestone is reminiscent of mandibularpatterns in wasp nests, prompted a literature search fordescriptions of possible fossil and Recent hymenopterananalogues. This revealed that many Tertiary-Quaternarycocoon-like trace fossils from localities in Europe, Africaand North and South America have been interpreted as thebrood chambers or cocoons of mining Hymenoptera. Mostundoubted examples of fossil brood chambers conform toonly two morphologies, both unlike the BembridgeLimestone trace fossils: flask-shaped and confluent with the

burrow-fill, attributed to digger wasps (Frenguelli, 1938a &b; Retallack, 1990: 201-202; Ritchie, 1987), or ovoid­cylindrical, with a detachable seal or cap at one end,attributed to solitary mining bees (Brown, 1934; Retallack,1984; Ritchie, 1987).

Although some Recent digger wasp larval cocoons(constructed within the brood chamber) figured by Evans(1966, fig. 205), and internal casts of Pliocene digger waspcocoons figured by Ritchie (1987), are approximatelyovoid-cylindrical, most of the Recent examples figured byEvans (1966) are slightly to prominently pointed at one end.Also, characteristically, they incorporate soil particles andsand grains. Unlike the Bembridge Limestone trace fossils,Pliocene casts figured by Ritchie (1987) were approxi­mately vertical when in situ and not confluent with theburrow-fills.

Unlike the Bembridge Limestone chambers, which seemto have been excavated or enlarged from within by back­filling the burrow, in the mining Hymenoptera the femaleparent excavates the burrow system and stocks and seals thebrood chamber from the outside, before laying an egg andtemporarily or permanently filling the burrow. A furthervery important characteristic of Recent, Quaternary (Petit­Maire, 1992) and Pliocene (Ritchie, 1987) hymenopteranbrood chambers, is that they occur close together, often ingreat numbers. This is due to the construction, by most taxa,of several chambers per burrow and the very large numbersconstructed at favoured sites by successive generations.

On the evidence presented, therefore, the BembridgeLimestone chambers are unlikely to be hymenopteran broodchambers. An alternative possibility, that they wereconstructed for hibernation or aestivation by an organismother than an insect, such as an annelid worm, would agreewith their wide size range, but a literature search has notfound a Recent analogue.

Although somewhat similar trace fossils from SouthGerman and Swiss Late Eocene-Miocene freshwaterlimestones were identified by Gergens (1861) andGutzwiller (1906: 31-33, pI. 4, figs 35-38) as leechcocoons, they are totally unlike fossil leech cocoonsdescribed by Manum, Bose & Sawyer (1991). These aremuch smaller, non-calcareous and have a net- or felt-likewall fabric. The latter feature is shown by a crushedspecimen from the Bembridge Limestone at Headon Hill(Hooker, Collinson, van Bergen, Singer, de Leeuw & Jones,1995, fig. 8).

5. NOMENCLATURE

Hooker (1986) referred Middle Eocene chambers of theBembridge Limestone type to the Lower Palaeozoic marineichnogenus Amphorichnus (Myannil, 1966). The ichno­genus is inappropriate, however, because it was based onmuch larger, vertical ?actiniid sea anemone living-burrows(Pemberton, Frey & Bromley, 1988). They display noorganized surface texture and by definition are character­ised by a distal, nipple-like pointed protrusion.

TRACE FOSSILS FROM THE LATE EOCENE, S ENGLAND 31

The ichnofossil generic name Celliforma that Brown(1934) proposed for fossil brood chambers attributable tomining Hymenoptera, was redefined by Retallack (1984)for those which, when entire, have a flat or conical seal atthe proximal end, which bears spiral or concentric grooveson its inner surface. Therefore this name too, is inappro­priate for the Bembridge Limestone chambers.

Either of the genera Chelonienovum and OphidienovumKuntz 1983, based on specimens from the French MiddleEocene, may be valid for the middle size range ofBembridge Limestone chambers, which overlap the statedsize ranges of these genera. Entire specimens of all fourgenera described by Kuntz (1983) are symmetricallyrounded at both ends, but compared to the BembridgeLimestone chambers the diameters are slightly smaller inproportion to the lengths. In common with the BembridgeLimestone chambers, Kuntz's specimens display a helical­linear surface texture and some are ruptured terminally.Because the nomenclature was not critical to the presentstudy, reference of the Bembridge Limestone chambers toone or more of Kuntz's genera has not been confirmed byexamination of the original material, the location of whichis unknown. Although these form genera were based onsupposed fossil reptile eggs, their use for the BembridgeLimestone chambers would not exclude a different inter­pretation. Their use, however, would involve their transferfrom body fossil to trace fossil nomenclature. In light of thenew English data, a critical and rigorous in situ revision ofthe French material is needed.

A major unresolved problem hindering systematicdescription and naming of these chambers, possibly as adistinct form of cocoon-like trace fossils, is whether or notthe lobate-linear surface textures are integral parts of thechambers, and thus diagnostic features. If they are, theywould provide a unifying characteristic allying theBembridge Limestone chambers with other European andNorth American Palaeogene chambers displaying similarsurface textures.

6. CONCLUSIONS

Ovoid-cylindrical calcitic or limestone trace fossils,approximately 30 mm long and 11 to 18 mm in diameter,

occur sparsely distributed in association with land snailsand freshwater snails in exposures of pedogenically­modified limestones in the Late Eocene BembridgeLimestone Formation at the western end of the Isle ofWight. The ovoid-cylindrical trace fossils were approxi­mately horizontal chambers excavated below the surface ofthe sediment. Rare specimens are hollow calcitic shellslined by crystalline calcite, but most are calcitic orsecondarily-cemented micritic internal casts, with orwithout a chalky surface film or micritic coat. Three speci­mens are attached by the distal end to a short burrow-fill.The organism escaped by rupturing one end of the chamber,possibly that adjacent to the burrow-fill. A surface ornamentcomprising lobes and composite lobate ridges, often alignedto form circumferential or helical lineations, may either betool marks made during excavation of the chamber, orinfaunal feeding traces. Although cited in the literature astropical land snails' eggs, these chambers bear littleresemblance to the eggs of Recent tropical land snails.Although similar trace fossils from the Tertiary-Quaternaryof other countries have been identified as the broodchambers of mining Hymenoptera, such as digger wasps,the chamber shape, mode of excavation and sparseoccurrence of the Bembridge Limestone chambers areuncharacteristic of the brood chambers of Recent miningHymenoptera. Possibly, therefore, they were made byanother kind of insect for pupation, or by an unknownorganism for hibernation or aestivation.

ACKNOWLEDGEMENTS

Our thanks to colleagues who allowed us to study or retainspecimens from the Bembridge Limestone and abroad, alsofor their valuable observations, to Dr Roland Goldring,University of Reading, for advice on interpretation of thesurface textures and nomenclature, and to the late MrRaymond E. Cumberland for generously and expertlyphotographing specimens at his own expense. We aregrateful to Professor Colyn Crane-Robinson, Professor ofBiochemistry, University of Portsmouth, for translatingrelevant parts of Myannil's description and discussion ofAmphorichnus. This is PRIS Contribution No. 604 for E. A.Jarzembowski.

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Manuscript received 9 April 1997; revised typescript accepted 14 July 1997