BIVALVIA. 165 



prominentibus ; lunula elongato-lmiceolatd, profunda ; ano angmto, elongato ; cardine 

 incrassato, unidentato, altera hidentato ; de^itibus obsolete sulcatis ; marginibus tenuiter 

 crenulatis. 



Shell transversely or ovately triangular, compressed, slightly inequilateral, 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. 



Lengthy 1 inch ; height, f ths of an inch. 



Localities. Huntingbridge [Edwards). 



France: Grignon, &c., Calcaire grossier [Deshages). 



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 in 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 lamellae 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 shghtly 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 hemileia, 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. This variety is from Brook and White Cliff Bay. 



5. Crassatella gibbosula, Beshayes. PL XXIIl, fig. 15 a — c. 



Crassatella gibbosula, Besh. Coq. Foss. des Env. de Par., vol. i, p. 37, pi. v, 



figs. 5, 6, 7, 1824. 



Spec. Char. " C. Testa ovatd, tumido-gibbosd {?) ; angulo antico eminentissimo ; 

 lamellis transversis exiguis proeminentibus, et postice tuberculo minimo seriatim inter ceptis ; 

 lunula profunde lanceolatd." — Beshayes. 



Shell elongate, transversely subquadrangular, or irregularly trapezoidal ; very inequi- 

 lateral ; pedal side rounded ; siphonal side produced, angular, and slightly pointed ; lamellae 

 sharp, prominent, and distant ; lunule distinct. 



Length, If ths inch; height, Ifth inch. 



