MO MOLLUSCA. PSAMMOBIADJ5. Astaetjs. 



it is known in the north of Scotland by the trivial name of " Brown circular 

 furrowed northern Cockle" — a descriptive epithet we have not heard of, and 

 which seems somewhat different from the usual provincial appellations. 



501. A. Danmonice. — Shell transversely ovate, with strong, 



regular, equidistant, concentric smooth ridges. 



Venus Dan. Mont. Test. Brit. Sup. 45. t. xxix. f. 4 Crassina sulcata, 



Turt. Biv. Brit. 131. t. xi. f. 1, 2 — English and Scottish coasts. 



Length an inch, breadth an inch and a quarter ; shell white, with a dark- 

 brown cuticle ; beaks nearly central, inclining, below which is a lanceolate 

 depression ; margin within glossy and crenulated ; teeth, two in each valve. 



* Margin plain. 



— 502. A. Scotica. — Shell transversely ovate, with strong, re- 

 gular, equidistant, concentric, smooth ridges. 



Venus Scotica, Maton and Ilackelt, Linn. Trans, viii. pt. 1. t. ii. f. 3. 



Mont. Test. Brit. Supp. 44 — Crassina Scotica, Turt. Biv. Brit. 130. 

 t. xi. f. 3, 4— Various parts of the coast, from Devon to Zetland. 



Length T 7 5 ths, breadth an inch ; white with a brown cuticle. It is princi- 

 pally distinguished from the preceding by the greater compression of the 

 ventral margin, the shortness of the lunule, and in the inside being less 

 rough, and the margin entire. 



503. A. compressa. — Shell subtriangular, rounded in front ; 



beaks very prominent, and inclining ; obsoletely and irregularly 



sulcatcd transversely. 



Venus compressa, Mont. Test. Brit. Sup. 43. t. xxvi. f. 1 — Maton and 

 Rackctt, Linn. Trans, viii. t. ii. f. 2 — Cyprina compressa, Turt. Biv. 

 Brit. 13C. t. xi. f. 20-23 — Coast of Scotland. 



Diameter about half an inch ; shell white, with a brown cuticle ; cartilage 

 slope but little rounded ; the depression in front of the beaks sudden. While 

 the figure in the Linn. Trans, above quoted belongs to this species, the de- 

 scription is that of A. sulcata. I possess dead valves from St Andrew's Bay 

 upwards of an inch and three-tenths in length. Is this distinct from Cras- 

 sina semisulcata of Dr Leach, Annals of Philosophy, xiv. 204. ? Even by the 

 aid of authentic specimens, I have failed to procure a specific difference. 



EXTINCT SPECIES. 



I. A. lurida — Transversely oblong, convex, depressed, with many trans- 

 verse undulations ; lunette elliptical, sharp ; margin crenulated within, near- 

 ly straight ventrally.— Sower. Min. Conch, t. exxxvii. f. 1 Inferior Oolite. 



2. A. clegan-s — Transversely oblong, convex, depressed, with many small 

 transverse costa?, lunette cordate ; margin crenulated within.— Sower. Min. 

 Conch, t. exxxvii. f. 3 — Inferior Oolite. 



3. A. cuneaia — Subcordate, acuminated, gibbose, with small transverse 

 costae; lunette cordate; margin entire within. — Sower. Min. Conch, t.cxxxvii. 

 f. 2.— Upper Oolite. 



4. A. plana — Nearly orbicular, depressed, surface plain ; lunette elongated, 

 acute, deep; margin entire.— Sower. Min. Conch. 179. £ 2.— Crag? 



5. A. obliquata Obovate, transversely depressed ; with many oblique con- 

 centric striae upon the surface ; margin crenulated. — Sower. Min. Conch- 

 t, clxxix. f. 3 In Crag. 



