50 Mr. R. J. L. Guppy on 
anteriorly somewhat produced and subangular; posteriorly 
high, with a decided obtuse angle formed by a low keel 
running from the umbo, on the upper and posterior side of 
which keel the shell is covered with a black epidermis. Valves 
flattened, white, rather fragile, marked with concentric striz 
of growth, which are worn smooth on the disk and umbones, 
but towards the ventral margin are covered with a yellowish- 
brown wrinkled epidermis. Length 85 millims., height 60, 
thickness 80. 
Closely allied to MW. fragilis, which, indeed, appears to have 
been confounded with it. The details of the hinge are some- 
what similar to those of the hinge of Hemémactra gigantea ; 
but the postcarinal area resembles that of Schizodesma. 'The 
latter feature is much developed in our shell, and is remark- 
able for its black epidermis, that of the other portions of the 
shell bemg of a hght brown. 
VII.—Notice of some Marine Shells found on the Shores of 
Trinidad. By R. J. LecoMerE Gurpry, F.L.S., F.G.S., Ke. 
(Plate VII. figs. 3 & 4.] 
Purpura trinitatensis, Guppy. 
A solid, ovate, yellowish, subrimate shell, adorned with 
numerous rounded spiral ridges, which are crossed by fine 
imbricating strie: whorls about 6, with four spiral rows of 
obtuse elongated tubercles, of which the two upper rows are 
much the largest, the superior one forming the angle of the 
whorls : suture hidden by a row of stout curved and reflected 
lamella, of which there are about three above each of the 
tubercles on the angle of the whorl: spire conic, sharp: 
mouth pink within, and often ornamented with two or three 
more or less interrupted spiral red or chestnut lines correspond- 
ing to the external rows of tubercles: aperture oval, with a 
small and decided posterior canal forming the successive sutural 
lamellee; anterior canal open and a little reflected: pillar-lip 
smooth, flattened or hollowed out, bright pink ; outer lip den- 
ticulate, obsoletely striate within. Height 40 millims., greatest 
breadth 27, longest diameter of aperture 26. 
Hab, Gulf of Paria, 
A species somewhat resembling P. mancinella, but with a 
sharper spire and a more decided striation. The sutural 
lamellee are well developed, like those of P. coronata. There 
is a strong’ idge round the base, : 
