446 
MOLLUSC A. VENERIDiE. Cythebea. 
519- C. orhicidata. — Orbicular, compressed and cancellated ; 
beaks snjall, with a minute cordiform impression in front. 
Venus orb. Mont. Test. Brit. Sup. 42. t. xxix. f. 7— Cyprina orbiculata, 
Turt. Biv. Brit. 138. — Dunbar, Mr Laskey. 
Diameter fths of an inch ; white ; margin plain ; two approximating teeth, 
and one transverse, and rather remote where the margin is angular. 
EXTINCT SPECIES. 
1. C. lentiformis. — Orbicular, depressed, with concentric, reflected, minute, 
imbricated ridges ; posterior slope depressed, terminated by an angle at the 
margin — Venus exoleta, Park. Org. Bern. iii. 189. V. lent. Sower. Min. 
Conch, t. cciii — Crag. 
2. C. Scutellaria. — ManU Geol. 203. t. xxv. f. 2. — Plastic Clay. 
Gen. CXXVIII. VENUS.— Shell suborbicular, inequilater- 
al ; hinge with three diverging teeth in each valve, the mid- 
dle one in the left valve strong and bifid. 
^ Margin within crenulated. 
520. V. verrucosa. — Shell tumid, heart-shaped, with numer- 
ous concentric ridges, broken into tubercles by longitudinal 
grooves at both extremities. 
O 
Pectunculus omnium, crassissimus. List. Conch, t. cclxxxiv — Concha^ 
cinerea, Borl. Corn. 275. t. xxyii. f. 32. — V. ver. Linn. Syst. i. 1130.-^ 
V. erycina, Penn. Brit. Zool. iv. 94. t. liv. f. 48. — V. ver. Don. Brit, 
Shells, t. xliv. ikTon/. Test. Brit. 112. Turt. Biv. Brit. 140 Eng- 
lish and Irish shores. 
Length two inches and a quarter, breadth a*little more ; rufous ; strong ; 
depression before the, beaks heart-shaped, the posterior, or cartilage depres- 
sion, distinctly displayed only on the left valve ; the ridges are sharp, reflect- 
ed and striated, and, towards the beaks the furrows are striated longitudinal- 
ly ; the margin crenulated within. 
521. V. cassina. — Shell slightly compressed and heart-shaped, 
with numerous concentric entire ridges. 
Linn. Syst. i. 1130 — ^V. erycina worn, Penn. Brit. Zool. iv. t. liv. f. 48. 
A ^V. lactea, Don. Brit. Shells, t. cxlix — V. cass. Maton and Rac- 
kett.^ Lin. Trans, viii. 79. t. ii- f. 1. Turt. Biv. Brit. 141. t. ix. f. 1 — 
Various parts of the coast. 
Diameter about two inches ; whitish ; ridges irregular in size, curving to- 
wards the hinge ; left valve at the ligament depressed and striate ; margin 
sometimes very obtuse. — This species is distinguished from the preceding by 
being less tumid, and by the ridges being entire. 
522. V. reflexa. — Shell compressed, dorsal margin behind the 
beaks nearly straight ; concentric ridges rising into thin plates 
re tr ally, where they are waved and deflected. 
Laskey., Wern. Mem, i. 384. t. viii. f. 1. Mont. Test. Brit. Sup. 40. 
Flem. Encyc. Edin. vii. 95. t. ccvi. f. 1. Turt. Biv. Brit. 142* t. x. f. 1, 
2,~Various parts of the coast from Devon to Zetland. 
