348 CRETACEOUS MOLLUSCA. 
Pecten Asellus. (Tab. XXVIII. fig. 5.) 
Spec. Cuar.—Suborbicular, radiated, squamose ; radii about ten, acute ; ears 
distinct, long and narrow, squamose at the edge. 
Well-distinguished by its long, narrow, free or distinct ears ; only one speci- 
men has fallen under our notice. 
Plagiostoma Hoperi, var. (Tab. XXVIII. fig. 21.) 
This variety strongly resembles Lima Santonensis of D’Orbigny. The species 
varies much in form as well as in the number of strie. 
Ostrea virgata. (Tab. XXVII. fig. 1.) 
Spec. Cuar.—Orbicular, convex, ornamented with numerous, branching, thin 
ridges ; surface otherwise nearly smooth, 
Remarkable for the thin ribs on the surface, by which, although the specimen 
is very imperfect, this shell is readily defined. 
MOLLUSCA GASTEROPODA. 
Dentalium? difforme. (Tab. XXIX. fig. 10.) 
Sprec. Cuar.—Tube irregular, ribbed; ribs about seven, prominent, rounded, 
crossed by indistinct lines of growth ; mouth small. 
Although this shell is irregular and strongly ribbed, yet its general form is 
that of a Dentalium; it tapers too quickly for a Serpula, and shows no mark of 
having been attached to any other body. 
Occurs in chalk marl. 
Hipponyx ? (Pileopsis?). (Tab. XXVII. fig. 8.) 
We have not seen the free valve of this shell, and cannot therefore determine 
the species. The gradual progress of the animal in changing its position is well 
shown. Similar specimens occur in the neighbourhood of Valognes in Normandy. 
Emarginula affins. (Tab. XXVII. figs. 20 & 25.) 
Spec. Cuar.—Conical, obtuse, with many thin ribs connected by regular lines 
of growth ; mouth oval. 
The striz between the ribs, which give a cancellated figure to most of the 
