144 Couthouy's Monograph on 
Thracia corbuloides, Kiener, Icon. p. 4. Gen. Tura- 
cia, (Montacuti citat. exclus.) tab. 2, f. 2; tab. 1. 
pro animali. - 
Description. Shell oval-oblong, transverse, some- 
what ventricose, sub-diaphanous by reason of its little 
thickness; inequilateral, the posterior side being the 
longer, very inequivalve, corbuliform, right valve the 
larger, covered with a thin, strongly adherent, dark 
grey epidermis, very rough to the touch, m conse- 
quence of a minute granulation which covers the 
whole surface, and under a magnifier resembles sha- 
green ; beaks large, protuberant and cordiform, curving 
slightly backwards, the summit of the right one ex- 
cavated to receive that of the left. The: cardinal 
edge is thin, having on the posterior side a nymphal 
callosity, projecting inwardly and receiving a ligament 
partly internal and partly external. The anterior 
extremity is rather obtusely rounded, basal margin with 
rather a prominent outward curve in its middle por- 
tion, posterior extremity broadly and irregularly trun- 
cated, somewhat compressed; an obtuse ridge ex- 
tends obliquely from the beaks to the lower poste- 
rior margin, and on the right valve a rather less 
prominent ridge runs from the beak to the middle of 
the truncation. The incremental strie are frequent, ir- 
regularly concentric, forming occasional ridges, which 
are most conspicuous at the truncated extremity. "The. 
internal color is milk-white and glossy, except toward 
the margin, outside of the palleal i impressions. Anterior 
muscular impression long and narrow, with a sort of in- 
dentation at its upper end; posterior rather small, 
