208 
CONCHIFERA. 
Cyrena. 
3. Cyprina equalis. —The Equal Cyprina, pi. LXXXV. 
fig. 7. 
Venus equalis. Sowerby, I. p. 59, pi. 21. 
Sub-orbieular, convex ; beaks obtuse, incurved ; hinge very 
strong; surface covered with numerous concentric striae, and 
a few shallow linos of growth ; substance of the shell very 
thick. 
From the Crag, Suffolk. 
4*. Cyprina planata. —The Plain Cyprina, pi. LXXXV. 
fig. 8 . 
C. planata. Sowerby, VII. pi. 619. 
Nearly orbicular and sub-cordiform ; gibbose; beaks ob¬ 
tuse ; on the posterior side a furrow, emanating from the back 
of the beaks, terminates on the margin ; surface with shallow, 
unequal linos of growth. 
Tlio London Clay, Nuneham, Brentford, and Bracklesham. 
5. Cyprina Morrisii. —Morris’s Cyprina, pi. LXXXVI. 
fig. 17. 
C. Morrisii • Sowerby, VII. pi. G20, fig. 1. 
Sub-orbicular; moderately gibbose; beaks obtuse, incurved ; 
surface with shallow* concentric linos of growth ; back rather 
straight; base arcuated. 
The London Clay, Ilerno Bay, Watford, Plumstoad, and 
Reading. 
G. Cyprina angulata. —The Angulated Cyprina, pi. 
LXXXV. fig. 10. 
Venus angulata. Sowerby, I. p. 145, pi. G5. 
Transversely ovate ; beaks short, very obtuse, and incurved ; 
anterior side with a slight longitudinal ridge, and a very little 
truncated ; surface smooth. 
The Greensand, Blackdown. 
7. Cyprina transversa. —The Transverse Cyprina, pi. 
XXXV. fig. 3. 
C. Morrisii. Var. Sowerby, VII. pi. G20, figs. 2 , 3. 
Transversely ovate, gibbose ; beaks obtuse, slightly incurv¬ 
ed ; anterior side short and rounded ; posterior side elongated; 
back arcuated, and bending suddenly downwards, forming an 
angle where it moots the basal Hue ; an elevation extends from 
the beaks to the posterior margin ; surface smooth, with un¬ 
equal shallow lines of growth. 
The London Clay, Watford. 
8. Cyprina rostrata. — The Beaked Cyprina, pi. 
LXXXVI. fig. 18. 
C. rostrata. Sowerby, Geo. Tr. 2 d Ser. IV. p. 341, pi. 17, 
fig. 1 . 
Obliquely triangular; beaks large, much produced, and in¬ 
curved, projecting nearly in a Hue with the margin, and under 
them the side is very concave, hollow ; dorsal line very little 
curved ; posterior side considerably lengthened, and narrowed 
at the extremity, with a gentle ridge running from the beaks 
to the margin ; basal line arcuated ; surface rather smooth. 
The Greensand, Blackdown. 
9. Cyprina rustxca. —The Rude Cyprina, pi. LXXXVI. 
fig. 31. 
C. rustica. Sowerby, II. p. 217, pi. 196. 
Sub-orbicular, transverse, gibbose ; beaks obtuse, a concave 
space under thorn ; anterior side narrowed ; dorsal line nearly 
straight; anterior side large and rounded ; base arcuated ; 
surface smooth ; lines of growth rather strongly marked. 
Red Crag, Sutton, and the Coral Crag, Ramshot. 
10 . Cyprina vulgaris. —The Common Venus, pi. 
LXXXVI. fig. 29. 
C. vulgaris . Brown, Ill. Rec. Conch. Brit. p. 93, pi. 37, 
fig. 1, and pi. 38, fig. 11. 
Obliquely sub-orbicular, gibbose ; beaks rather large ; sur¬ 
face covered with numerous fine, concentric stria? ; dorsal and 
basal line arcuated; posterior side a little narrowed. 
The Pleistocene Marine Formations, on the Clyde; and the 
Coral Crag, Ramshot. 
Sub-Division II.—FLUVIATILE. 
Shell covered with a spurious epidermis, and the hinge 
provided with lateral teeth. 
Genus XXXIII.—CYRENA.— Lamarck. 
Sholl sub-orbicular, sub-trigonal, equivalve, ventricose, 
inequilateral, and solid; external surface covered with 
a strong epidermis, and the umbones usually decorticat¬ 
ed ; throe cardinal, and two remote lateral teeth in each 
valve ,* in one valve the posterior one is situate near the 
primary teeth, the anterior one being more remote, and placed 
beforo the ligament; in tho opposite valve a deep groove 
intervenes between two teeth, one of which is large, and the 
other nearly obsolete; two lateral remote muscular impres¬ 
sions ; pallial impression destitute of a sinus; ligament 
external. 
1. Cyrena trigonula.— The Trigonal Cyrena, pi. 
LXXXVI. fig. .5. 
Cyrena trigonula. Wood, Mag. Nat. Hist. VII. p. 275, 
fig. 45, a and b. 
Ovately trigonal, sub-equilatoral, thick, with sub-imbricated 
transverse lines of growth, with three cardinal teeth in each 
valve ; lateral teeth largely sorrated ; umbones obtuse ; mar¬ 
gin plain. 
Found in the Lacustrine Formations at Stutton, where it 
is very abundant. 
2. Cyrena cycladiforme.— The Cyclas-formed Cyrena, 
pi. LXXXIII. fig. 28. 
C. cycladi/orinis . Deshayes, Coq. Fos. pi. 19, figs. 7, 8, 9. 
Ovate; anterior side rounded, posterior side somewhat 
acuminated; surface smooth. 
The London Clay, Barton. 
3 Cyrena deperdita. —Tho Lost Cyrena, pi. LXXXVI. 
fig. 2. 
Cyclas deperdita. (?) Sowerby, III. p. 139, pi. 162, fig. 1. 
Transversely oval, rather gibbose ; umbonate ; anterior side 
a little angulated; surfaco with elevated, irregular lines of 
growth ; hinge with throe bifid cardinal teeth and two lateral 
ones, which are sometimes striated perpendicularly. 
The Plastic Clay, Charlton and PJumstead. 
4. Cyrena cuneiformis. —The Wedged-shapod Cyrena, 
pi. LXXXVI. fig. 3. 
Cyclas cuneiformis. Sowerby, II. p. 140, pi. 172, figs. 2, 3. 
