MUSEUM OF COMPARATIVE ZOOLOGY. 307 
sense, as has been done by some conchologists; since, if it has the right to be 
used at all, it is entitled to take precedence of Thracia as the primary name of 
the group. 
There are several species of Thracia, not including the plaited Cyathodonta 
of Conrad, formerly referred to Thracia, which inhabit the southern and south- 
eastern coasts of the United States and adjacent waters. Most of them have 
not been definitely recognized hitherto. They are: — 
Thracia Stimpsoni, n. s. 
Thracia corbuloidea Blainville. 
Thracia distorta Montagu. 
Thracia phaseolina Lamarck. 
Thracia Stimpsoni, n. s. 
Thracia Stimpsoni is a magnificent species, nearly as large as T. Conradi, 
and of which but one right valve has yet been obtained, between Tampa and 
Tortugas in 28 fms. in the Gulf of Mexico. It differs from T. convera Wood, 
which is its nearest relative, in its whiter and much more coarsely granulose 
surface, in its more horizontal posterior hinge-margin not rounded off at its 
posterior end, and by two strong ribs, one of which extends parallel with the 
posterior hinge-line, bounding a narrow smooth depressed marginal area, and 
having a wider depressed broad ray on the outer and lower side; the other rib 
extends from the beak to the lower posterior angle of the rostrum; in front 
of it the shell is much depressed, behind it elevated for a space extending to 
the depressed ray above mentioned; the middle basal margin is more produced 
than in T. convexa, and the pallial sinus is shallower and less angular. The 
other proportions are about the same as in T. convexa. 
The specimen in the National Museum is 65.0 mm. long, and is named in 
honor of the late Dr. William Stimpson. 
Thracia corbuloidea Buainvit1ez. 
Thracia corbuloidea Blainville, comparing excellently well with the series 
in the Jeffreys collection, has been obtained by the U. S. Fish Commission 
in from 15 to 50 fms. off the coast of North and South Carolina, generally 
about twenty miles from shore. I have it also from Key West, collected by 
Hemphill. 
Thracia distorta Monracu. 
Thracia distorta Montagu, has been sent me from Honduras by Mr. Charles 
T. Simpson, who was formerly resident there. It does not exactly agree with 
any particular specimen from British seas, but differs from most of them less 
than they differ among themselves. It is possible that this may be the same 
