CVPIUNA. 



CONCHIFERA. 



207 



truncated ; back arcuateJ ; base nearly straight ; lunette 

 lanceolate and obscure ; surface with strong lines of growth. 

 The London Clay, Barton. 



18. Cytherka suB-uoTU.NDA.^Tho Ilalf-Round Cytherea, 

 pi. LXXXIV. fig. 29. 



C. sub-rotunda. Sowerbv, Geo. Tr. 2d Ser. IV. 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. Cytuerea PLANA. — The Plain Cytherea, pi. LXXXIV. 

 fig. 27. 



Feniis 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. Cytuerea transversa. — The Transverse Cytherea, 

 pi. LXXXVI. fig. 22. 



Venus transversa. Sowerby, V. p. 25, pi. 422, fig. 1. 



Transversely elongated, oblong-ovale ; gibbose ; posterior 

 side a little pointed ; surface smooth, with a few concentric 

 lines of growth ; beaks considerably incurved ; lunette elongat- 

 ed and narrow. 



21. Cytuerea rotdndata. — The Rounded Cytherea, pi. 

 LXXXIV. fig. 7. 



Venus linceolata. Sowerby, V. p. 25, pi. 422, fig. 2. 

 Brander, fig. 91. 



Nearly orbicular; gibbose; surface with numerous, deep, 

 regular, concentric stria;. 



The London Clay, Barton. 



Genus XXXL— ARTEMIS.— PoZi. 



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. Aute.mis lentifokmis. — The Lentil-shaped Artemis, 

 pi. LXXXV. fig. 5. 



A. lenti/ormis. Wood, Cat. Vcntu lentiformis. Sowerby, 

 III. p. 235, pi. 203. 



Orbicular, compressed ; anterior side slightly angulatcd, and 

 somewhat compressed; surface with numerous, fine, imbricated, 

 narrow, concentric ridges. 



The Red Crag, Walton Naze. 



2. Artemis exolet.\. — The Worn Artemis, pi. LXXXV. 

 fig. C. 



A. exoleta. Brown, Illust. Rec. Conch. Brit. p. 92, pi. 3G, 

 figs. 1, 3, 19,20. 



Orbicular, lentiform, moderately convex ; anterior 8ide with 



a nearly obsolete longituilinal 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 stri;e. 

 The Pleistocene Marine Formation, Dalrauir and Ayr. 



3. .\rtemis sinuata. — TheSinuated Artemis, pi. LXXXV. 

 fig. 4. _ 



A. lincta. Brown, 111. Rec. Conch. Brit. p. 92, pi. 30, 

 figs. 2 and 4. 



Lentiform, slightly elongated, and moderately gibbose ; sur- 

 face with numerous, very fine, filiform, concentric stria; on the 

 disk, and sub-lamellated on the sides ; posterior side with a 

 longitudinal furrow ; luuotto cordiform, with extremely fine, 

 concentric, longitudinal striic. 



The Red Crag, Walton, AValton Naze ; and the Coral Crag, 

 Ramshot. 



This species is at once distinguished from any of the former two, liy 

 the strise being much finer, and by its lengthened form. 



4. Artemis parva. — The Small Artemis, pi. LXXXV. 

 fig. 9. 



A. parva. Brown, Manchester Geo. Tr. I. p. 1, 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, Vale of Todmorden, Yorkshire. 



Genus XXXIL— CYPRINA.— ZrtTOa>ri-. 



Shell ventricose, 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. 

 LXXXV. fig. 1. 



C. cuneata. Sowerby, Geo. Tr. 2d Ser. IV. p. 341, pi. IG, 

 fig. 19. 



Transversely 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 ; base nearly straight ; surface even, 

 with shallow lines of growth ; valves deep ; substance of the 

 shell thin. 



The Greensand, Blackdown. 



2. Cyprina triangularis. — The Triangular Cyprina, pi. 

 LXXXV. fig 2. 



C. cuneata. Var. Sowerby, Geo. Tr. 2d Ser. IV. pi. 16, 

 fig. 19, the smaller figure. 



Triangular, elongated ; beaks almost central ; aides nearly 

 equal, the posterior one sub-truncated below ; surface smooth, 

 with distant, shallow lines of growth. 



The Greensand, Blackdown. 



