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 strije finer. 
Fig. 6 we called the C. ohliqua, 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, L 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 striae are observable 
by the aid of a lens ; inside smooth, extremely glossy, usually 
of a purple hue, frequently shaded with golden-yellow, or 
orange-bufiF, 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. Austin’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,* hut 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. 11 ; 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 very dis- 
tant from the cardinal ones ; margins crenated. 
Found on most of the coasts of Great Britain and Ireland. 
2. Donax rubra, pi. XXXIX, f. 13. 
Donax ruhra, 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 difierent 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 be the anterior side, and it can only lead to confusion to make 
an exception in this genus. 
