44)4 MOLLUSCA. VENERID^. Cypeina. 
Brit. 114. — C. isl. TurU Biv. Brit. 135.-— Not uncommon on all parts 
of the coast. 
This is the largest British bivalve shell, measuring sometimes 13 inches 
in circumference, and, exclusively of the animal, weighing upwards of 9 
ounces ; it is slightly truncated retrally ; the ligament at the beak is lodged 
in a deep cavity ; there is no lunette in front of the beaks. At St Andrew’s 
it is called Daikie, and in Zetland Cuvie. 
511. C. triangularis. — Subtriangular, smooth, -with a length- 
ened cordiform depression in front of the beaks. 
Venus tri. Mont. Test. Brit. 577- t. xvii. f. 3 — C. tri. Turt. Biv. Brit. 
136. t. xi. f. 19, 20. — South of England and Dublin bay. 
Diameter about half an inch ; yellowish-white ; strong, with a few obsolete 
concentric ridges ; the beaks are produced, and the slope is nearly equal on 
both sides ; in one valve two teeth, and a curved lateral one, in the other 
three teeth and a curved lateral one. 
512. C. minima. — Suborbicular, compressed, with broad, 
smooth, transverse ribs. 
Venus min. MmU Test. Brit. 121. t. iii. f. 3.— C. min. Turt. Biv. Brit. 
137. — Southern coasts of England. 
Length a quarter of an inch, breadth rather more ; flesh-coloured, with 
two red spots near the beaks, and two near the margin, connected by two 
white lines ; glossy, strong. Dr Turton assigns to this species only two 
hinge teeth besides the lateral ones. 
EXTINCT SPECIES. 
1. C. aqualis. — Uniformly ’con vex, obcordate, or nearly circular, covered 
with numerous transverse concentric striae ; thick, particularly in the middle ; 
margin acute, extended, entire ; cicatrix obscure. — Venus equalis. Sower. 
Min. Conch, t. xxi. — In Crag. 
2. C. angulata Obtusely cordate, broader than long, beak short angular, 
rising on the posterior side, which is slightly truncated, smooth ; margin en- 
tire ; larger hinge-teeth placed at an angle of about 60° — Venus ang. Sower. 
Min. Conch, t. Ixv. — In Green Sand. 
3. C. rustica. — Suborbicular, gibbose, smooth ; posterior side obscurely de- 
fined, convex, with a thick lateral tooth. — Venus rustica. Sower. Min. Conch, 
t. cxcvi.— In Crag. 
Gen. CXXVII. CYTHEREA. — Shell suborbicular or trans- 
verse, unequilateral ; hinge, on the right valve, of three 
diverging teeth and one transverse and detached at the 
side under the lunule ; three diverging teeth in the other 
valve, with an adjacent transverse cavity anteriorly ; sy- 
phon marks distinct. 
51S. C. Shell ovately-subtrigonal, smooth, glossy, 
with slight concentric lines of growth ; a lanceolate lunule raised 
in the middle. 
