CONCHACEA.] 



MOLLUSCA. 



97 



This species is not uncommon in the Frith of Forth, and at 

 Color Cots, near Tynemouth, Northumberland. 



In the first edition, we considered the three figures referred 

 to as distinct species, but on comparing various specimens, we 

 are now inclined to look upon them as mere varieties. 



Fig. 7 was thought a decided species by my late friend Dr. 

 Leach, and who named it C. convexiuscula, MSS., p. 8. It is 

 considerably more convex, with the striae finer. 



Fig. 6 we called the C. obliqua, from its oblique form, and 

 being stronger and more inflated than the others. 



Genus 18 Capsa. — Lamarck. 



Shell transverse, equivalve, inequilateral; valves close all 

 round ; one valve with two cardinal teeth, divergent from a 

 point close to the umbo ; destitute of lateral teeth ; in the 

 opposite valve one distinct, bifid, cardinal tooth, with two dis- 

 tant, nearly obsolete, lateral teeth ; ligament external, entirely 

 situate on the anterior side of the umbones ; two, not very 

 deeply defined muscular impressions in each valve ; pallial im- 

 pression with a large sinus. 



1. Capsa complanata, pi. XXXIX, f. 10. 



Donax complanata, First Ed., pi. 17, f. 10; Montagu, p. 

 106, pi. 5, f. 4 ; Maton and Rackett, p. 75 ; Fleming, p. 433 ; 

 Turton, Biv., p. 125, pi. 7, f. 13, 14. 



Shell subtriangular, transversely elongated; umbones obtuse; 

 smooth, and extremely glossy ; of a pale or golden-yellow, or 

 faint lilac-colour, frequently spotted and blotched with reddish- 

 brown, or fawn ; a broad, paler, generally immaculate ray 

 emanates at the umbones, and terminates on the margin, 

 which is frequently edged with a ferruginous shade ; in some 

 specimens faint indications of transverse stria? are observable 

 by the aid of a lens ; inside smooth, extremely glossy, usually 

 of a purple hue, frequently shaded with golden-yellow, or 

 orange-butf, especially near the umbones, and sometimes with 

 transverse zones of pale bluish-purple ; teeth small, especially 

 the lateral ones ; margin destitute of crenulations. 



This rare species is met with at Milton Sands ; on the coasts 

 of Devon, Dorset, Torbay, and Guernsey ; and has been met 

 with on the Irish coasts, at Connamara. 



2. Capsa castanea, pi. XXXIX, f. 12. 



Capsa castanea, Turton, p. 128, pi. 10, f. 13; Fleming, p. 

 434; Donax castanea, Montagu, p. 573, pi. 17, f. 2; Maton 

 and Rackett, p. 77. 



Shell strong, transversely elongated; umbones obtuse, slightly 

 inflected towards the anterior side; surface glossy, of a chestnut- 

 colour, with a few irregular, transverse, nearly obsolete wrinkles; 

 an arcuated ray of darker chestnut emanates at the umbones, 

 and terminates in the base, from whence to the posterior side 

 the colour is paler than on the other parts of the shell ; inside 

 smooth, glossy, and of a pale chestnut, with an indication of the 

 external ray on the margin ; hinge strong, with the teeth large, 

 in proportion to the size of the shell ; margin plain. Length a 

 quarter of an inch ; breadth three-eighths. 



Found at St. Austle's Bay, Cornwall, Penzance, and south 

 coast of Devonshire. 



2 B 



Section II. — Shells with one or two lateral teeth. 



Genus 19 — Donax Linnaeus. 



Shell transverse, trigonal, equivalve, inequilateral; outer sur- 

 face generally covered with a thin, horny epidermis ; anterior 

 side for the most part the shorter ; left valve with two more or 

 less distinct, cardinal teeth ; right valve with only one cardinal 

 tooth, which is generally cleft at its extremity; lateral teeth 

 variable, either two or one, very minute, and remote; two large 

 muscular impressions in each valve, and that of the mantle with 

 a large posterior sinus ; ligament external, and short. 



In some species there are two lateral teeth, one of which 

 being placed on each side of, and near to the primary teeth ; 

 one valve is provided with a linear, posterior process, remotely 

 situated from the other lateral teeth, and between which and 

 the margin of the shell, there is a groove for the reception of 

 the other valve ; the anterior lateral tooth can alone be distin- 

 guished, in each valve in other species, together with the linear 

 process ; in some species there are two lateral teeth in one 

 valve, the posterior one more remote than the anterior, while 

 in the opposite valve there are only slight indications of them ; 

 and in some species the lateral teeth are nearly obsolete. The 

 ligament is generally short, and in some instances very much 

 so ; the greater portion of it is situate anteriorly,* but in most 

 of the species a small portion of the ligament is likewise placed 

 behind the beaks. The shells of this genus are for the most 

 part wedge-shaped. 



1. Donax trunculus, pi. XXXIX, f. 11. 



Donax trunculus, First Ed., pi. 17, f. 1 1 ; Pennant, p. 93, 

 pi. 55, f. 45 ; Donovan, I, pi. 29, f. 1 ; Montagu, p. 103 ; Tur- 

 ton, p. 123 ; Fleming, p. 433 ; Forbes, p. 46. 



Shell somewhat compressed, transversely oblong, inequila- 

 teral, smooth, glossy ; umbones small ; very finely striated lon- 

 gitudinally ; covered with a very thin epidermis, generally of a 

 light yellowish hue, fasciated and radiated with purple, the radii 

 emanating from the beaks, and terminating on the basal margin; 

 sometimes quite plain ; inside most frequently partaking of the 

 colour of the exterior; teeth small, the lateral one not verv dis- 

 tant from the cardinal ones ; margins crenated. 



Found on most of the coasts of Great Britain and Ireland. 



2. Donax eubra, pi. XXXIX, f. 13. 



Donax rubra, Montagu, Sup., p. 38; Turton, Biv., p. 127, 

 pi. 10, f. 11 ; Fleming, p. 434. 



Shell cuneiform, smooth, and semitransparent, considerably 

 truncated at one end ; umbones prominent, but obtuse at the 

 points; surface of a reddish-flesh or claret-colour, but frequently 

 only coloured near the umbones ; inside glossy, and usually of 

 the same colour as the outside ; hinge with two teeth in each 

 valve, approximating towards the centre of the umbones ; mar- 

 gin plain. Length not an eighth of an inch. 



Inhabits deep water on different parts of the coast. Dr. 

 Turton says it is found abundantly in fine shelly sand at 

 Tenby. 



* Contrary to Lamarck, we consider the side in which the ligament is 

 situate to he the anterior side, and it can only lead to confusion to make 

 an exception in this genus. 



