Part 1

ILLUSTRATED INDEX

OF

BRITISH SHELLS.

CONTAINING

FIGURES OF ALL THE RECENT SPECIES,

With Names and other Information.

BY

G. B. SOWERBY, F.L.S.

LONDON:

SIMPKIN, MARSHALL, AND CO., PATERNOSTER ROW;

AND

THE AUTHOR, 9, PEMBROKE SQUARE, KENSINGTON.

1859.

* * * * *

PREFACE.

The first idea of this Work arose from the occasional use of Mr. Damon's 'Catalogue of the Shells of Great Britain and Ireland,' named after the 'History of British Mollusca,' etc. Here was, on one side, a very useful list of names, without figures or references to guide an inquirer to the species; and on the other, a very large and splendid Work, placed by its heavy price beyond the reach of Naturalists in general. There was nothing between the two; nothing within reach that would assist collectors of British Shells to name their acquisitions from ocean, beach, river, pond, or hedgerow. A public want seemed here to be discovered. It was thought that a list like the above, with a coloured drawing of every species, if produced at an available price, would supply that want. At first no more than this was thought of, but afterwards, as the preparations advanced, various suggestions were made tending to some extension of the plan. The results are here presented.

About 700 Figures in the Plates represent all the recognized species. They amount to 600, being 60 more than are admitted in the latest monograph. The greater part of these are either new or newly introduced as British. The rest are raised from varieties to species.

As the nomenclature used by Messrs. Forbes and Hanley in their great Work will be most generally adopted in this country, it is followed here with very few alterations; and the synonyms given (in italics) are selected from those which are most familiar and likely to be met with.

Some information is added respecting habits and localities, range of depth of marine species, and comparative abundance. The letters C., Cc., Mc., R., Rr., and Mr., signifying 'common,' 'extremely common,' 'moderately common,' 'rare,' etc., must be taken with great caution, especially the latter, as subject to continual change.

A list is given of British Fossil Shells identical with now living species.

A familiar description of British Mollusca and some peculiarities in their families and genera will, it is hoped, form a useful and suitable introduction to the names and figures. The Author's best thanks are due to his friends, Madame De Burgh, who has collected many beautiful shells; R. McAndrew, Esq., F.L.S., whose dredging experiences are so extensive; J. G. Jeffreys, Esq., F.R.S., etc., whose researches have resulted in so many additions to our Fauna; Mr. Brice Wright, the Naturalist, of Great Russell Street, and others, who have in the most liberal manner supplied him with specimens from which his drawings are taken. The loan of delicate and minute shells to authors and artists has so often proved disastrous, that nothing but a generous friendship, and a zealous love of Natural History, could have induced proprietors so freely to incur the risk.

* * * * *

INTRODUCTION

TO

SHELL-BEARING BRITISH MOLLUSCA.

A common garden Snail, observed crawling and feeding, is easily seen to possess a distinct head, upon which are four feelers or horns, with eyes at the end, and underneath which is a mouth; a broad disc, extending the whole length of the body, is the organ of locomotion; a spiral or coiled shell surmounts the whole.

If, on the other hand, an Oyster be opened, no distinct head, or place for eyes or mouth, can be seen, but only a seeming mass of pulp, with a round gristle in the centre (the muscle of attachment), the former enclosed in a soft skin with a double fringe round the edge (mantle), placed within a shell composed of two pieces.

All Mollusca are more or less completely represented by these two. The Snail and its class are named _Gasteropoda_ (abdomen-creeping), and their shells _Univalves_; the Oyster and its class, _Acephala_ (headless), and their shells _Bivalves_. We begin with the latter class at--

PLATE I.

_Pholadidæ_, or "Borers," 1-13, have the power of piercing and inhabiting holes in submarine wood, rocks, and stones. The hinder part of the body is lengthened out in the form of a double tube, with openings for the ingress and egress of fluids. _Teredo_, 1-6, has short valves, two pallets fixed at the sides of the siphons, and lines its hole with a shelly tube. _Pholas_ and _Pholadidea_, 8-13, have long valves and sometimes accessory plates. The shell of _Xylophaga_, 7, is like that of _Teredo_, but the animal has neither pallets nor tube.

_Gastrochæna_, 14, has a gaping shell, and encloses itself in a bottle-shaped covering of cemented stones and sand. _Saxicava_, 15, 16, _Venerupis_, 18, and _Petricola_, 17, burrow in sand, or live in holes of rocks.

_Myadæ_, or "Gapers," _Mya_, 19, 20, and _Panopæa_, 21, 21*, burrow downwards in sand and mud, their siphons protected by a coriaceous covering. Their shells are not closed all round, and those of _Mya_ have a spoon-shaped process in the hinge of one valve.

_Corbulidæ_, 22-28, have short siphons with fringed edges, and the foot protrudes through a hole in the otherwise closed mantle.

PLATE II.

_Poromya_, 1, 1*, and the beautiful pearly _Pandora_, 2, 3, might be included in the family of _Corbulidæ_. _Lyonsia_, 4, and _Thracia_, 5-10, represent the _Anatinidæ_. 11-18 are _Solenidæ_, or "Razor-shells." Solens burrow in deep holes in the sand, where they remain in a perpendicular position at a great depth below the surface, where yet their presence may be traced by the opening left. Their large muscular foot enables them to take great leaps when out of the holes.

PLATE III.

_Psammobia_, 1-4, and _Tellina_, 5-16, include some of our most beautiful shells. The animals have a large, fleshy, curved foot, and the mantle open and fringed. Their shells are provided with an external ligament, and teeth on the hinge. _Donax_, or "Wedge," 19, 20, has long, separated, fringed siphons. Besides the small external ligament, properly so called, the _Mactridæ_ have a triangular pit in the hinge of their shell, containing an elastic substance or spring, designed to resist the action of the adductor muscles. _Mactra_, 21-26, ends the Plate.

PLATE IV.

_Lutraria_, 1-3, is another genus of _Mactridæ_. The _Veneridæ_, 4-16 and 23, or "Venus" tribe, differ from it in not having the spring-holding pit. _Artemis_, 10, 11, is known by a large angular bend in the pallial impression; and _Cytherea_, 23, is distinguished from Venus by one tooth on the hinge standing out a little way from the central ones. _Astarte_, 17-22, belongs to the _Cyprinidæ_.

PLATE V.

Fig. 1-3 also represent genera of _Cyprinidæ_. They have no bend in the palleal impression. _Cardium_, or "Cockle," 4-13, presents a peculiarity in the foot, which is large and bent, and enables the animal to leap in a very lively manner. The family of _Lucinidæ_ occupy the remaining figures. _Lucina_ has a curious tongue-shaped doubling of the pallial impression.

PLATE VI.

The _Kelliadæ_, 1-15, are marine, while the _Cycladidæ_, completing the Plate, are fresh-water bivalves, and may be found in many ponds and rivers.

PLATE VII.

Of the _Unionidæ_, or "Fresh-water Mussels," _Unio_, 1-3, has teeth on the hinge, and _Anodon_, 4, has not: it is a thin shell. The foot of these molluscs is very large, and is used in cutting the animal's way through the mud in which it burrows. Of the marine, or true Mussels, _Modiola_, 6-9, and _Crenella_, 12-17, have a portion of the shell reaching beyond the point or apex, which in _Mytilus_ is terminal, 18-21. _Dreissina_, 5, is shaped like _Mytilus_, but lives in fresh-water docks. The _Mytilidæ_ attach themselves by means of horny threads spun from the foot, and called a "byssus."

PLATE VIII.

Shells of _Arcadæ_, 1-14, have the hinge characterized by a series of teeth on each side of the apex. _Nucula_, _Arca_, and _Pectunculus_ are easily distinguished. _Limopsis_, 14, has a spring pit between the two rows. Our figure of _Pinna_, 16, is from a young specimen: it grows to great size, and spins a very silky byssus. The shell of _Anomia_, 18, is fixed to rocks, etc., by means of a bony button passing through a hole or sinus in the lower valve. _Lima_, 22-24, has a light, thin shell, and its mantle is adorned with beautiful fringes. It swims rapidly through the water by the opening and shutting of its valves, and also has the habit, in seasons of rest, of protecting itself by a network or vest of marine fragments strung together by its byssal threads.

PLATE IX.

Contains the shells of our Pectens, or Scallops, 1-16. The animals swim like _Lima_, as above, and also spin a byssus.

The class _Brachiopoda_, 17-24, so named because what seem to be organs of locomotion consist of a pair of coiled, ciliated arms, ends the list of Headless Molluscs and their bivalve shells.

PLATE X.

Class _Pteropoda_, 1-4, contains minute Mollusca, with glassy shells variously formed, and wing-like expansions for swimming.

_Chiton_, 5-17, or "Coat of Mail," which may often be seen incrusting rocks, commences the _Gasteropoda_; although seemingly fixed, they are capable of locomotion, using the whole of the oval disc, which may be seen on turning them over, for the purpose. The same may be said of the "Limpet" tribe, _Patella_, 1-22.

PLATE XI.

This Plate commences with other forms of the Limpet tribe, _Fissurella_, 1, 2, with a hole at the top; _Puncturella_, 3, with a fissure near the top; and _Emarginula_, 4-6, with a slit at the margin. _Haliotis_, 7, or pearly "Ear-shell," leads to the _Trochidæ_, or "Tops," 8-27.

PLATE XII.

_Ianthina_, 1-4, is genus of oceanic molluscs, which are provided with a beautiful floating apparatus, on which the female carries her egg-bags.

_Neritina_, 5, and the _Paludinidæ_, 8-11, live in fresh-water. The animal of _Paludina_ is sprinkled all over with bright, golden specks. The _Littorinæ_, or "Winkles," 12-24, are marine, and frequent the shore among seaweeds. _Lacuna_, 25-32, belongs to the same family.

PLATE XIII., XIV.

Are small genera, various in their characters and habits, but reasonably included in the last family, _Littorinidæ_.

PLATE XV.

The animals of _Turritella_, 1-3, and _Cæcum_, 6, 7, are not unlike, although the shells are so different; eyes at the base of the tentacles, a short foot, and horny operculum. The somewhat similar animal of _Aporrhais_, 4, 5, is brilliantly coloured with gold and red. _Cerithium_, 8-10, differs from _Cerithiopsis_, 11-15, more in regard to the animal than the shell; the latter animal has a retractile proboscis, and its operculum is not spiral.

PLATE XVI.

_Chemnitzia_, 1-11, and _Truncatella_, 12, together with _Stylifer_, _Eulima_, and _Odostomia_, form the family of _Pyramidellidæ_. Notwithstanding the difference in the shells, the animals are very similar, having a retractile proboscis, and eyes immersed at the base of their tentacles.

The animal of _Natica_, 13-19, has a lobe on the upper part of the foot, reflected over the shell in front, and another lobe behind. The shells of _Laminaria_, 23, 24, are completely enveloped in similar lobes.

PLATE XVII.

The shells of _Odostomia_ are known by a fold in the inner lip of the aperture.

PLATE XVIII.

Two _Tritons_, 1, 2, are admitted for the first time as British, on what we consider fair evidence, although only two or three specimens have been taken off Guernsey. One of _T. nodiferus_ was incrusted by a truly British _Lepralia_. _Murex_, 3, is now familiar as an aquarian, as well as _Purpura_, 5. A milky secretion found in the head turns purple when exposed, and gives the celebrated purple dye. _Buccinum_, 7-13, includes the common "Whelk," 8. _Fusus Berniciensis_, 14, is among the rarest and most beautiful of our British shells.

PLATE XIX.

_Nassa reticulata_, 3, is a favourite inhabitant of the tank; it burrows in search of food among the pebbles, elevating its siphon above the surface. _Mangelia_, 4-26, has a similar long siphon. The shell of _Erato_, 27, is wrapped in the lobes of the animal's mantle, as is also that of _Cyprea_, 28, the latter presenting a beautiful object.

PLATE XX.

After _Tornatella_, 1, and _Ovula_, 2, 3, come _Bullidæ_, 4-27, including several genera differing remarkably in the shape and disposition of the lobes of their mantles, which in some instances, as in _Philine_, 20-25, cover the shell. The stomach of _Scapander_, 26, 27, is a remarkable kind of mill, composed of two bones, between which the food is ground. The shells of _Aplysia_, 28, and _Pleurotranchus_, 29, 30, are quite internal. _Spirula_, 31, belonging to the Cephalopodous or Cuttlefish tribe, is only introduced doubtfully, as there is no proof of the species living in our seas.

PLATE XXI., XXII., XXIII., XXIV.

These are occupied by shells of _Gasteropoda pulmonifera_, so named because they breathe air by a pulmonary cavity, instead of water by gills. The _Limnæadæ_, or fresh-water Snails, contained in Plate I., live in water, but breathe by exposing the pulmonary cavity to air at the surface. _Succinea_, Plate XXII., 1-3, lives by the sides of streams, sometimes immersed. _Conovulus_, 4-7, affects brackish marshes. Our common Slugs yield, on dissection, thin shells, which are concealed beneath the mantle, _Limax_, 9-12. The shells of _Testacellus_, 13, 14, are fixed near the end of the foot, outside. The glassy shells of _Vitrina_, 15, 16, do not enclose the whole Slug-like animal. The other genera of Land Snails have shells large enough to receive the animal when retracted and withdrawn for repose.

* * * * *

BRITISH FOSSIL SHELLS.

The following living species are also found in a fossil state in drift and strata of the British Isles. They are all enumerated in Mr. Searles Wood's monograph of the CRAG Mollusca.

The numbers refer to the species as figured in our Plates, Mr. Wood's nomenclature being inserted in italics when differing from ours.

Pl. I. Teredo 2. Pholas 11. Pholadidea 12. Gastrochæna 14, as _dubia_. Saxicava 15, 16. Venerupis 18. Mya 19, 20. Panopea 21, 21*, as _Faujasii_. Corbula 22, 23? Sphænia 25. Neæra 27.

Pl. II. Poromya 1. Pandora 2, as _inæquivalvis_, 3, as _pinna_. Thracia 7, 8. Solen, 13, 15. Solecurtus 18, as _Mactra strigilata_. Syndosmya, as _Abra_, 19, 22.

Pl. III. Psammobia 1, 3, 4. Tellina 5, 6, 7, 9, as _ovata_, 15, as _Balthica_, 16. Scrobicularia 18, as _Trigonella plana_. Donax 19, as _vittatus_. Mactra 20, 21, 22, as _ovalis_, 23, 25, 26.

Pl. IV. Lutraria 2. Tapes 7, 8. Artemis 11. Venus 12, 14, 15, 17. Astarte 18, 19, 20, 22, as _borealis_.

Pl. V. Cyprina 1. Circe 2. Isocardia 3. Cardium 6, 8, 9, 12, 13. Lucina 14, as _Loripes_, 15, as _Cryptodon flexuosum_, 16. Diplodonta 19. Clausina 20, as _Cryptodon f._

Pl. VI. Montacuta 1, 2, 3. Kellia 5, 6. Poronia 7, as _Kellia r._ Cyclas 16, 18. Pisidium 23, 24, 25, 26.

Pl. VII. Unio 2, 3. Anodon 4. Modiola 6, 9, 10. Crenella 13, 14, 15, 16. Mytilus 18, 19, 20.

Pl. VIII. Nucula 1, 5. Leda 6, 7. Area 9, 10, 11, as _pectunculoides_. Pectunculus 13. Avicula 15. Pinna 16. Ostrea 17. Anomia 18, 19, 20, 21. Lima 22, 23, 24.

Pl. IX. Pecten 1, 2, 5, 8, 9, 10, 11, 12, 13, 14.

Pl. X. Chiton 7, as _fascicularis_. Patella 18. Acme 23. Propilidium, as _Tectura_, 24. Dentalium 26, 27. Capulus 28. Calyptræa 29.

Pl. XI. Fissurella 1, as _græca_. Puncturella 3. Emarginula 5, 6. Trochus 8, 10, 11, 12, as _papillosus_, 15, 16, 17, 19. Margarita 21. Adeorbis 25. Scissurella 26.

Pl. XII. Paludina 9. Valvata 10. Littorina 14. Lacuna 27.

Pl. XIII. Rissoa 3*, as _Paludestrina subumbilicata_, 7, 11?, 13?, 15, 23, 27.

Pl. XIV. Rissoa 2, 9, as _Chemnitzia_. Aclis 24, as _Alvania ascaris_, 25, as _Chemnitzia n._

Pl. XV. Turritella 2. Aporrhais 4. Cæcum 6, 7. Cerithium 9, 10. Cerithiopsis, as _Cerithium_, 11. Scalaria 17, 19, 20. Eulima 22, 25.

Pl. XVI. Chemnitzia 1, 2, as _similis_, 4, 8. Natica 13, 17, as _Catena_, 19, as _Groenlandica_. Velutina 21. Trichotropis 26.

Pl. XVII. Odostomia 1, 8, as _plicata_, 9, as _plicata_, 10?, 12.

Pl. XVIII. Purpura 5. Buccinum 10? Fusus 15, as _Trophon_, 16, as _Tr._, 17, as _Tr. gracile_, 18, as _Tr. T._, 19, as _Tr. p._ Trophon 22, 24.

Pl. XIX. Nassa 1, 2. Mangelia, as _Clavatula_, 4, 5, 8, as _Philberti_, 9, 11, as _Boothii_, 12, 14, 15, 17?, 21, 22. Erato 27. Cypræa 28.

Pl. XX. Tornatella 1, as _Actæon tornatilis_. Ovula 3, as _Bulla_. Cylichna, as _Bulla_, 4, 5, as _regulbiensis_, 7, 9, 12. Bulla 19. Philine as _Bullæa_, 21, 22. Scaphander, as _Bulla_, 26.

Pl. XXI. Limnæa 1, 4, 7, 11. Planorbis 18, 24, as _complanatus_, and in the upper fresh-water formation, all except 9, 11.

Pl. XXII. Succinea 1, 3. Conovulus 5, and in the more recent fresh-water deposits, all except 7 and 13 to 16.

Pl. XXIII. Helix 19, 22, and upper fresh-water, all except 1, 12, 14, 15, 24, 25, 26.

Pl. XXIV. Upper fresh-water deposits, all except 16, 24.

* * * * *

INDEX TO THE GENERA.

Referring to Plates and Figures.

Achatina, XXIV. 24. Aclis, XIV. 23, 25. Acmæa, X. 22, 23. Acme, XXIV. 26. Adeorbis, XI. 25. Akera, XX. 16. Amphispira, XX. 14, 15. Ancylus, XXI. 14-17. Anodonta, VII. 4. Anomia, VIII. 18-21. Aplysia, XX. 28. Aporrhais, XV. 4, 5. Arca, VIII. 18-12. Argiope, IX. 20, 23. Artemis, IV. 10, 11. Assiminea, XIII. 1, 2. Astarte, IV. 17, 22. Avicula, VIII. 15. Azeca, XXIV. 23.

Balea, XXIV. 17. Barleeia, XIV. 12. Bithinea, XII. 6, 7. Buccinum, XVIII. 8-13. Bulla, XX. 17-19. Bulimus, XXIV. 1-4.

Calyptræa, X. 29. _Capulus_, Pileopsis. Cardium, V. 4-13. Carychium, XXII. 8. Cæcum, XV. 6-7. _Cemoria_, Puncturella. Ceratisolen, II. 11. Cerithiopsis, XV. 11-15. Cerithium, XV. 8-10. Chemnitzia, XVI. 1-11. Chiton, X. 5-17. Circe, V. 2. _Clavatula_, Mangelia. Clausilia, XXIV. 18-21. Clausina, V. 20-22. Cochlodesma, II. 10. Conovulus, XXII. 4-7. Corbula, I. 22-24. Crania, IX. 24. Crenella, VII. 12-17. Cyclostoma, XXIV. 25. Cyclas, VI. 16-20. Cylichna, XX. 4-13. Cypræa, XIX. 28. Cyprina, V. 1. Cytherea, IV. 23.

Dentalium, X. 26, 27. Diodonta, II. 16, 16*. Diplodonta, V. 19. Donax, III. 19, 20. Dreissina, VII. 5.

Emarginula, XI. 4-6. Euomphalus, XIV. 17, 18. Ervillia, III. 17. Eulima, XV. 22-26. Eulimella, XIV. 26-30.

Fissurella, XI. 1, 2. Fusus, XVIII. 14-19.

Galeomma, VI. 14, 15. Gastrochæna, I. 14.

Haliotis, XI. 7. _Helix_ (Zonites), XXII. 17-29. Helix, XXIII. 1-29. _Hinnites_, Pecten, IX. 1. Hippothyris, IX. 17. Hyalæa, X. 1.

Ianthina, XII. 1-4. Isocardia, V. 3.

Jeffreysia, XIV. 13-16.

Kellia, VI. 5-8.

Lachesis, XVIII. 6. Lacuna, XII. 25-32. Lamellaria, XVI. 23, 24. Leda, VIII. 6, 7. Lepton, VI. 9-13. Lima, VIII. 22-24. Limax, XXII. 9-12. Limnæa, XXI. 1-11. Limopsis, VIII. 14. Littorina, XII. 12-24. Lucina, V. 14-18. Lucinopsis, IV. 9. Lutraria, IV. 1-3. Lyonsia, II. 4.

Mactra, III. 21-26. Mangelia, XIX. 4-26. Margarita, XI. 21-24. _Marginella_, Erato. _Megathyris_, Argiope. Modiola, VII. 6-11. Montacuta, VI. 1-3. Murex, XVIII. 3, 4. Mya, I. 19-20. Mytilus, VII. 18-21.

Nassa, XIX. 1-3. Natica, XVI. 13-19. Neæra, I. 26-28. Neritina, XII. 5. Nucula, VIII. 1-5.

Odostomia, XVII. 1-31. Ostrea, VIII. 17. Otina, XVI. 25. Ovula, XX. 2, 3.

Paludina, XII. 8, 9. Pandora, II. 2, 3. Panopæa, I. 21, 21*. Patella, X. 18-21. Pecten, IX. 1-16. Pectunculus, VIII. 13. Petricola, I. 17. Phasianella, XI. 27. Philine, XX. 20-25. Pholas, I. 8-11, 13. Pholadidea, I. 12. Physa, XXI. 12, 13. Pileopsis, X. 28. Pilidium, X. 24. Pinna, VIII. 16. Pisidium, VI. 21-28. Planorbis, XXI. 18-28. Pleurobranchus, XX. 29. _Pleurotoma_, Mangelia. Poromya, II. 1, 1*, IX. Propilidium, X. 25. Psammobia, III. 1-4. Puncturella, XI. 3. Pupa, XXIV. 5-16. Purpura, XVIII. 5.

Recluzia, XVI. 20. Rissoa, XIII. 3-28; XIV.

Saxicava, I. 15, 16. Scalaria, XV. 16-20. Scaphander, XX. 26, 27. Scrobicularia, III. 18. Scissurella, XI. 26. _Segmentina_, Planorbis, XXI. 27, 28. Skenea, XIV. 19-22. Solen, II. 12-15. Solecurtus, II. 17, 18. Spirialis, X. 2-4. Spirula, XX. 31. Stylifer, XV. 21. Succinea, XXII. 1-3. Syndosmya, II. 19-22. Sphænia, I. 25.

Tapes, IV. 4-8. Tellina, III. 5-16. Terebratula, IX. 18-20. Teredo, I. 1-6. Testacellus, XXII. 13, 14. Thracia, II. 5-9. Tornatella, XX. 1. Trichotropis, XVI. 26. Triton, XVIII. 1, 2. Trochus, XI. 8-20. Trophon, XVIII. 20-24. Truncatella, XVI. 12. Turritella, XV. 1-3. Turtonia, VI. 4.

Unio, VII. 1-3.

Valvata, XII. 10, 11. Velutina, XVI. 21, 22. Venerupis, I. 18. Venus, IV. 12-16. _Vertigo_, Pupa. Vitrina, XXII. 15-16.

Xylophaga, I. 7.

Zonites, XXII. 17-29. Zua, XXIV. 22.

PLATE I.

TEREDO. Pierces and inhabits wood.

Fig.

1. T. NAVALIS, _Linn._--_T. Batavæ._--Herne Bay, R. Pallets shelly, crescented; valves with auricles extended sidewise; tube long.

2. T. NORVEGICA, _Spengl._--_T. Bruguieri._--Port Patrick, Teignmouth, etc., Mc. Pallets shelly, not crescented; auricles not extended.

3. T. MEGOTARA, _Hanl._--_T. nana_ (young).--Herne Bay, Devon, Swansea, etc., R. Pallets shelly, spade-shaped; auricles raised and expanded.

4. T. BIPENNATA, _Turt._--Ireland, Scarborough, etc., R. Pallets horny, long; auricles lobed.

5. T. MALLEOLUS, _Turt._--Torquay, Rr. Pallets shelly, mallet-shaped; valves narrow.

6. T. PALMULATA, _Lamk._--_T. bipalmulata._--Floating wood, Ire., S. Eng. Pallets horny, short; valves small, shaped like _T. navalis_.

XYLOPHAGA. In fixed and floating timber.

7. X. DORSALIS, _Turt._--Ayrs., Dubl., Exm., Scarb., etc., C. Two dorsal plates, no tube, no pallets.

PHOLAS. Pierces and inhabits stone.

8. P. DACTYLUS, _Linn._--_P. hians_, _P. callosa_.--Eng., Scot., Ire., C. Dorsal plates four; hinge pitted.

9. P. CANDIDA, _Linn._--Eng., Scot., Ire., C. One dorsal plate; valves not beaked.

10. P. PARVA, _Penn._--_P. callosa_, _P. tuberculata_.--Salcombe, Belfast, Cornwall, etc., M. C. One dorsal plate; valves beaked.

11. P. CRISPATA, _Linn._--_P. bifrons._--Hastings, Liverp., Scarb., Dubl., Forth, etc., C. No dorsal plate; valves broad, beaked, with oblique division.

13. P. STRIATA. Rare and doubtful as British. Valves closed.

PHOLADIDEA. Pierces and inhabits stone.

12. P. PAPYRACEA, _P. Loscombiana_, _P. Goodalli._--S. Devon, N. Ire., R. Valves closed, with a cup. _P. lamellata_, Turt., when young, not closed; no cup.

GASTROCHÆNA. Bores and inhabits stone, thick shells, etc.

14. G. MODIOLINA, _Lamk._--_G. Pholadia_, _G. hians_, _Mya dubia_, _Mytilus ambiguus_, _Pholas faba_.--Torbay, Birterbuy, Galway, Weymouth, etc. Valves thin, gaping, enclosed in bottle-shaped tube.

SAXICAVA. Bores and inhabits stone.

15. S. RUGOSA, _Linn._--_Mytilus r._, _Hiatella r._, _S. gallicana_, _S. pholadis_, _Byssomya pholadis_, _Mya byssifera_.--Eng., Scot., Ire., C. Valves oval.

16. S. ARCTICA, _Linn._--(_Mya_) _Hiatella a._, _Anatina a_., _Hiatella minuta_, _Solen minutus_, _S. rhomboides_, _Agina purpurea_, _Solen p._--Eng., Scot., Ire., C. Valves rhomboidal; angle serrated.

_Omitted._--S. fragilis, _Nyst._ _Not_ the young of _S. rugosa_. Vigo Bay.

PETRICOLA. Inhabits stone.

17. P. LITHOPHAGA, _Retz._--_P. striata_, _costellata_, _rocellaria_, _ruperella_, Lamk., _Mya_ and _Sphænia decussata_.--Cork, Bristol, R. as British.

VENERUPIS. Bores and inhabits stone.

18. V. IRUS, _Linn._ (Donax).--_Tellina cornubiensis_, _Cuneus foliaceus_, _Petric._, and _Pullastra_, I.--In limestone at Plymouth and other southern coasts. Wedge-shaped.

MYA. Burrows in mud and sand.