MOLLUSCA. 
91 
CONCHACEA.] 
7. Venus Casina, pi. XXXVI, f. 15.* 
Clausina Casina, First Ed., pi. 20, f. 15;* Venus Casina, 
Linne, p. 1130 ; Pennant, pi. 54, f. 48 a; Maton and Rackett, 
p. 79) pi- 2, f. I ; Turton, Biv., p. 141, pi. 9) f. 1 ; Montagu, 
Sup., p. 47 ; Fleming, p. 446 ; Forbes, p. 52 ; Venus lactea, 
Donovan, pi. 149. 
Shell suborbicular, very thick, heavy, and rather inflated ; 
provided with numerous, transverse, much elevated, laminar, 
concentric ridges, subcrenulated on the posterior side ; the 
intervening furrows with nearly obsolete, transverse striae ; um- 
bones not prominent, acute, and turned to the anterior side, 
beneath which is a cordiform, short, deeply defined lunule, 
covered with longitudinal, fine striae; colour yellowish-white, or 
pale rusty-brown ; inside dull white ; margin very broad, finely 
crenated, greatly thickened on the edge, and covered with a 
dark blackish-brown coloured, laminated epidermis. 
Found in the British Channel, off the Isle of Man ; many 
parts on the coasts of Ireland ; and at Caithness, Scotland. 
8. Venus reflexa, pi. XXXVII, f. 12, 13. 
Clausina rejiexa. First Ed., pi. 19, f. 12, 13 ; Venus rejlexa, 
Laskey, Wernerian Mem., I, p. 384, pi. 8, f. 1; Montagu, Sup., 
p. 40 and 168; Turton, Biv., p. 142, pi. 10, f. 1, 2; Fleming, 
p. 446. 
Shell suborbicular, rather strong, subcompressed ; umbones 
small, considerably inflected ; beneath them an oblong, cordi- 
form lunule, elevated in the centre, and of a reddish-brown 
colour; posterior or cartilage side broad; whole surface covered 
with numerous, inequidistant, transverse, thin, reflected, laminal 
ridges, which are covered with extremely fine, decussated strise ; 
on the anterior side they are very sharp, more elevated and 
undulated, and turn in a contrary direction to other parts, 
sometimes with a small intervening one, irregularly disposed; 
the furrows are beset with numerous, nearly obsolete, longitu- 
dinal stria;, which can only be seen by the aid of a lens; colour 
pale yellowish-brown or cream-white, with two or three inter- 
rupted, longitudinal, reddish-brown radii, consisting of sagittate 
spots, which point towards the umbones ; inside white ; hinge 
with three strong teeth in both valves, the middle one slightly 
bifid ; a small tubercle situate on the posterior side of the teeth, 
under the areola, in the right valve, with an indentation in the 
opposite one for its reception ; margin finely crenated. 
Found in the Frith of Forth; south coast of Devon; and 
Bantry Bay, Ireland. 
9. Venus fasciata, pi. XXXVI, f. 10. 
Clausina fasciata. First Ed., pi. 20, f. 10; Venus fasciata, 
Donovan, V, pi. 170; Pennant, IV, p. 203; Turton, Biv., p. 
146, pi. 8, f. 9; Fleming, p. 447 ; Forbes, p. 52; Maton and 
Rackett, p. 80; Venus paphia, Montagu, p. 110. 
Shell subtriangular, strong, subcompressed; umbones pro- 
minent, nearly central, sbarp-pointed, contiguous, and much 
turned to the anterior side, with a considerably elongated, shal- 
low, ovate lunule beneath them, and extremely fine, longitudi- 
nally oblique striae ; anterior side acutely hollowed, the length 
of the lunule, at the base of which the valves are somewhat 
peaked ; cartilage or posterior side nearly flat, with a lancealate 
depression ; surface plain, white, yellow, or orange, but most 
commonly with several radiations of reddish-brown, pale lilac, 
or rusty-brown, which are sometimes interrupted, and beauti- 
fully mottled in some specimens ; with upwards of a dozen 
broad, flat, transverse, reflected ribs, unequal both in number 
and breadth, being narrowed and more acute at the posterior 
side, sometimes regular, and nearly equidistant, at others, 
arranged in threes, or pairs, and in some instances an inter- 
vening, narrow, sharp rib between the sets; inside smooth, 
glossy, white, pale flesh-colour, or lilac, sometimes with a brown 
mark at one end; margins much thickened, and finely crenated. 
Length a little more than seven-eighths, but more commonly 
only six-eighths of an inch. 
Found on almost all the British and Irish coasts, particularly 
those with a gravelly or clayey bottom. 
10. Venus ovata, pi. XXXVII, f. 11. 
Timoclea ovata. First Ed., pi. 19, f. 11 ; Timoclea Pennantii, 
Leach, MSS., p. 9; Venus ovata, Montagu, p. 120; Pennant, 
IV, p. 97) pi. 56, f. 56 ; Maton and Rackett, p. 85, pi. 2, f. 4 ; 
V mus Pennantii, Forbes, p. 52 ; Cytherea ovata, Fleming, p. 
445. 
Shell subovate, subcompressed, oblique, nearly equilateral; 
pale brown or yellowish, frequently mottled with rusty-brown ; 
with strong, longitudinal, divergent ribs, crossed by fine, trans- 
verse strise, which produce tubercular elevations on the ribs, 
and give a beautifully cancellated appearance to the surface ; 
umbones almost central, slightly inflected, with a subcordiform 
lunule under them, which is somewhat elevated in the centre ; 
inside glossy, white, sometimes of a pale flesh-colour, being 
frequently pale purple in the centre of the valves ; margins 
slightly crenated. Length varying from half an inch to three- 
quarters. 
Found on most of the British and Irish coasts. We met with 
a variety of this species in the estuary of the Clyde, in which 
the longitudinal ribs were set in pairs. 
Genus 11. — Cytherea. — Lamarck. 
Shell equivalve, generally more or less equilateral or obtusely 
trigonal, and transverse or ovate; smooth, or variously striated; 
with three or more short, divergent, cardinal teeth ; and one 
anterior, approximate, lateral tooth in both valves, situate near 
the primary teeth ; two remote, lateral, muscular impressions, 
united by a pallial impression, which is interrupted by a broad, 
transverse sinus; ligament external. ' 
1. Cytherea Chione, pi. XXXVII, f. 2. 
Cytherea Chione, First Ed., pi. 19, f. 2; Lamarck, V, p. 566; 
Fleming, p. 444; Turton, Biv., p. 160, pi. 8, f. 11; Venus 
Chione, Montagu, p. 115; Donovan, I, pi. 17; Maton and 
Rackett, p. 84; Chione coccinea, Leach, MSS., p. 8. 
Shell strong, obliquely ovate, subcompressed ; covered with 
a thick, extremely smooth, glossy, chestnut-coloured epidermis, 
with a few concentric wrinkles; more or less radiated with 
deeper coloured chestnut ; umbones obtuse, placed considerably 
to one side, beneath them a strong, large, cordiform lunule ; 
inside of a glossy, bluish-white ; margins thick, rounded, with a 
hollow betwixt them when closed ; pallial impressions with a 
very broad, transverse sinus, acuminated at tbe point. Length 
three inches ; breadth three and three-quarters. 
This very beautiful shell inhabits the coasts of Dorsetshire 
and Cornwall. Young shells are frequently of a beautiful, deep 
rosy flesh-colour. 
