THRACIA. 229 



Devon and Cornwall appear to be the only counties of 

 England which furnish us with this interesting bivalve : 

 in the former it is occasionally taken at Dawlish (Clark), 

 Plymouth (Montagu), and other parts of the southern 

 coast, in the latter at Falmouth (Couch). 



In Ireland it is taken on the Dublin coast and in Belfast 

 Bay (Thompson); Birterbuy Bay (Barlee). 



T. coNVEXA, Wood. 



Subtriangular, inflated, cuneiform in convexity, ferruginous, 

 subequilateral ; dorsal edges peculiarly sloping : umbones ex- 

 cessively prominent : hinge plate extremely narrow. 



Plate XVI. figs. 1, 4. 



Ligula distorta, Mont, Test. Brit. Suppl. (not his original species), p. 166. 

 Mya convexa. Wood, General Conch, p. 92, pi. 18, f. 1. — Turt. Conch. Diction. 



p. 100.— Index Testa ceol. pi. 2, Mya, f. 3. 

 Anatina convexa, Turt. Conch. Dithyra Brit. p. 45, pi. 4, f. 1, 2. — Brit. Marine 



Conch, p. 41. 

 Amphidesiua convexum, Flem. Brit. Anim. p. 431. 



Thracia convexa, Couthouy, Bost, Jouni. N. H. vol. ii. p. 140. — Brown, 111. 

 Conch. G.B.p. 110, pi. 44, f. 3.— Hanl. Recent Shells, p. 22, 

 „ decUvis, Macgill. Moll, Aberd. p. 296. 



Perhaps the most important feature of this rare shell, 

 which, to the best of our knowledge, has never yet been 

 found elsewhere than in the British islands, where it is 

 reckoned one of our rarest species, is its peculiar inflation ; 

 the lesser valve (for it is inequivalve, although less strikingly 

 so than our other Thracias) almost vying in that particular 

 with the larger. The shape is oval triangular, the umbones 

 being remarkably prominent. The texture is thin but not 

 remarkably so, and under a slight ochraceous epidermis, 

 the colour varies from pale ferruginous to orange buff 

 colour. The surface is not shagreened, but merely traversed 

 by ^le concentric wrinkles of increase, which, however, are 



