BIVALVIA. 165 
prominentibus ; lunuld elongato-lanceolatdé, profundd ; ano angusto, elongato ; cardine 
incrassato, unidentato, alterd bidentato; dentibus obsoleté sulcatis ; marginibus tenuiter 
erenulatis. 
Shell transversely or ovately triangular, compressed, slightly imequilateral, finely and 
regularly sulcated ; pedi-lateral margin obtuse and rounded; opposite side angulated and 
obscurely sinuated ; beaks small ; lunule deep and elongated ; corselet large and lanceolate ; 
hinge broad and thick; teeth obsoletely sulcated ; margins finely crenulated. 
Length, \ inch; height, $ths of an inch. 
Localities. Wuntingbridge (Hdwards). 
France: Grignon, &c., Calcaire grossier (Deshayes). 
In ‘ Les Coq. foss. des Env. de Par.’ M. Deshayes has given three varieties to the 
above name, and in the supplement to that work he has elevated one of them to the rank 
of a species. The same differences appear to exist im specimens from our own deposits ; 
and as they seem much more abundant in the Paris Basin I imagine that M. Deshayes 
may have better materials for determination than we have. The present shell is distin- 
guished by the lamella or ridges, which are numerous, prominent, and cover the entire 
surface. These are obtuse ; the interspaces are about the same width as the ridges. The 
shell is slightly inequilateral, the siphonal side being a little the longer, pointed and less 
deep ; the pedal side is shorter and higher, so that one side is not much larger than the 
other. In perfect specimens the ridges are carried over the flattened anal area, and the 
crenulations extend over the entire edge of the inner margin, except the truncated portion 
of the siphoni-lateral side. 
Fig. 1, Pl. XXIII, represents a specimen from Mr. Edwards’s Collection which has the 
MS. specific name of emileia, but which, I think, is not specifically distinct. I have, 
therefore, united it as a variety under that name. It differs principally in being sulcated 
only over the umbonal region. his variety is from Brook and White Cliff Bay. 
5. CRASSATELLA eIBBosuLA, Deshayes. Pl. XXIII, fig. 15 a—e. 
CRASSATELLA GIBBOSULA, Desh. Coq. Foss. des Env. de Par., vol. i, p. 37, pl. vy, 
figs. 5, 6, 7, 1824. 
Spec. Char. “C. Testdé ovata, tumido-gibbosd (?); angulo antico eminentissimo ; 
lamellis transversis exiqguis proeminentibus, et posticé tuberculo minimo seriatim interceptis ; 
lunuld profunde lanceolata.” —Deshayes. 
Shell elongate, transversely subquadrangular, or irregularly trapezoidal ; very inequi- 
lateral ; pedal side rounded ; siphonal side produced, angular, and slightly pointed ; lamellie 
sharp, prominent, and distant ; lunule distinct. 
Length, \Zths inch; height, 13th inch. 
