Cypkina. 
CONCIIIFERA. 
207 
truncated; back arcuated; base nearly straight; lunette 
lanceolate and obscure ; surface with strong lines of growth. 
The London Clay, Barton. 
18. Cytherha sub-rotunda.-^-TIio Half-Round Cytherea, 
pi. LXXXIY. fig. 29. 
C. sub-rotunda. Sowerby, Geo. Tr. 2 d Ser. IY. p. 341, 
pi. 17, fig. 2 . 
Lenticular, nearly orbicular; much compressed; lunette 
narrow and lanceolate ; back arcuated ; beaks obtuse; surface 
smooth. 
The Greensand, Blackdown. 
19. Cytherea plana.— The Plain Cytherea,pi. LXXXIY. 
fig. 27. 
Venus planus. Sowerby, I. p. 58, pi. 20 , lower figs. 
Somewhat elongated, its length slightly exceeding its 
width; sub-depressed; anterior side a little concave under 
the beaks, and rounded below ; posterior side arcuated ; sur¬ 
face smooth ; lunette lanceolate. 
The Greensand, Blackdown and Lyme Regis. 
20. Cytherea tkansversa.— The Transverse Cytherea, 
pi. LXXXYI. fig. 22 . 
Venus transfer8(t. Sowerby, Y. p. 25, pi. 422, fig. 1 . 
Transversely elongated, oblong-ovate ; gibbose; posterior 
side a little pointed; surface smooth, with a few concentric 
lines of growth ; beaks considerably incurved ; lunette elongat¬ 
ed and narrow. 
21. Cytherea rotundata.— The Rounded Cytherea, pi. 
LXXXIY. fig. 7. 
Venus linceolata. Sowerby, Y. p. 25, pi. 422, fig. 2 . 
Brander, fig. 91. 
Nearly orbicular; gibbose; surface with numerous, deep, 
regular, concentric strise. 
The London Clay, Barton. 
Genus XXXI.—ARTEMIS.— Poli. 
Shell nearly orbicular and lenticular, externally and con¬ 
centrically grooved ; beaks much turned to one side, beneath 
which is a short, strongly-marked, cordiform depression ; three 
cardinal teeth in each valve, two of which are contiguous, and 
the other divergent, which is broad in the right valve, cleft in 
the centre, to receive that of the opposite valve, which is 
slender, with a small lateral and closely approximated tooth • 
pallial impression with a large, oblique, and straight-sided 
sinus; cartilage external. 
1 . Artemis lentiformis. —The Lentil-shaped Artemis, 
pi. LXXXY. fig. 5. 
A. lentiformis. Wood, Cat. Venus lentiformis. Sowerby, 
III. p. 235, pi. 203. 
Orbicular, compressed ; anterior side slightly angulated, and 
somewhat compressed; surface with numerous,fine, imbricated, 
narrow, concentric ridges. 
The Red Crag, Walton Naze. 
2 . Artemis exoleta. —The Worn Artemis, pi. LXXXY. 
fig. G. 
A. exoleta. Brown, Illust. Rec. Conch. Brit. p. 92, pi. 36, 
figs. 1, 3, 19, 20. 
Orbicular, lentiform, moderately convex ; antorior side with 
a nearly obsolete longitudinal furrow ; surface with numerous 
concentric filiform stria?, those on the disk, and as far as the 
umbones, smooth, slightly depressed, and thin and elevated on 
the sides ; lunette cordiform, with fine longitudinal stria?. 
The Pleistocene Marine Formation, Dalmuir and Ayr. 
3. Artemis sinuata. —ThoSiuuated Artemis, pi. LXXXY. 
fig. 4. 
A. lincta. Brown, Ill. Rec. Conch. Brit. p. 92, pL 36, 
figs. 2 and 4. 
Lentiform, slightly elongated, and moderately gibbose ; sur¬ 
face with numerous, very fine, filiform, concentric stria* on the 
disk, and sub-lamellatcd on the sides; posterior side with a 
longitudinal furrow ; lunette cordiform, with extremely fine, 
concentric, longitudinal stria*. 
The Red Crag, Walton, Walton Naze ; and the Coral Crag, 
Ramshot. 
This species is at once distinguished from any of the former two, by 
the stria* being much finer, and by its lengthened form. 
4. Artemis parva. —The Small Artemis, pi. LXXXY. 
fig. 9. 
A. parva. Brown, Manchester Geo. Tr. I. p. l, pi. 7 , 
fig* 77. 
Nearly orbicular; surface smooth, with a few distant, dis¬ 
tinct lines of growth; diameter somewhat more than an eighth 
of an inch. 
The Coal Shale, Yale of Todmorden, Yorkshire. 
Gen rs XXXII.—CYPRINA.— Lamarck. 
Shell ventrioose, equivalve, inequilateral, sub-orbicular, ob¬ 
liquely heart -shaped; umbones obliquely curved anteriorly ; 
three cardinal teeth in each valve, approximated at their bases, 
and divergent above, with a posterior lateral tooth remote from 
the primary teeth; external surface covered by a thick, rough, 
dark, horny epidermis; each valve with two lateral, remote, 
muscular impressions; pallial impression with a slight sinus; 
ligament external, inserted into a deep, marginal, posterior, 
dorsal sinus. 
1 . Cyprina cuneata. —The Wedge-shaped Cyprina, pi. 
LXXXY. fig. 1 . 
C. cuneata. Sowerby, Geo. Tr. 2 d Ser. IY. p. 341, pi. 10 , 
fig. 19. 
3 ransversely elongated, wedge-shaped ; posterior side 
lengthened and acuminated ; anterior side short, concave 
under the prominent and curved beaks; lunette heart-shaped 
and hollow ; back convex ; baso nearly straight; surface even, 
with shallow lines of growth ; valves deep; substance of the 
shell thin. 
The Greensand, Blackdowm. 
2. Cyprina triangularis. —The Triangular Cyprina, pi. 
LXXXY. fig 2. 
C. cuneata . Yar. Sowerby, Geo. Tr. 2 d Ser. IY. pi. 16, 
fig. 19, the smaller figure. 
Triangular, elongated; beaks almost central; sides nearly 
equal, the posterior one sub-truncated below ; surface smooth, 
with distant, shallow lines of growth. 
The Greensand, Blackdown. 
