﻿330 CONRAD'S DESCRIPTIONS OF 



4. Ostkea denticulifera. PI. 34, figs. 1 and 8. Irregular, moderately thick, 

 indented, but not plicated; upper valve flattened ; hinge area wide, with a transverse 

 ridge at the base of the fosset ; lower valve moderately capacious ; upper margins 

 denticulated ; muscular impressions large. 



EXOGYRA, Say. 



Exogtra interrupta. PI. 34, fig. 15. Adhering, thin ; lower valve with inter- 

 rupted radiating costse ; upper valve entire, with a thickened margin. 



A small species. The lower valves in all the specimens adhere to other shells and 

 nearly conceal the exterior character. 



PULVINITES, Defrance. 



Pulvinites argentea. PI. 34, fig. 5. Transversely subovate, compressed ; per- 

 forated valve slightly concave; foramen oval, from its upper margin a channel 

 extends to the apex ; substance of shell silvery, thin ; cardinal plate broad, with 

 about thirteen radii or teeth ; the lower valve presents within the appearance of two 

 muscular impressions, the one above the other, the former striated. 



The present species of this rare genus is allied to P. Adansonii, but differs from 

 the figures of that species in having a broader hinge plate, and much less curvature 

 of the posterior margin. It closely resembles an Anomia exteriorly. P. Adansonii 

 characterises the Upper Cretaceous rocks of Europe. 



ANOMIA, Lin. 



Anomia sell^eformis. PI. 34, fig. 6. Suborbicular, with a short fold anteriorly 

 towards the hinge line ; posterior side with a profound plication. 



Length I inch. 



There is but one valve of this species in Dr. Spillman's collection, and per- 

 haps other specimens may exhibit a considerable variation from the saddle-shape 

 character. 



GASTEROPODA. 



STROMBUS, Lin. 



Strombus densatus. PI. 35, fig. 14. Lip expanded, very thick; costas disap- 

 pearing on the middle of the volution ; labrum suddenly thickened, with a groove 

 behind the raised margin ; a calcareous deposit sometimes'coats the whole shell, rising 

 into an oblique, thick, prominent ridge, the upper margin of which is on a line with 

 the apex. 



APORRHAIS, Petiver. 



Aporrhais decemlirata. PI. 35, fig. 11. Spire elevated, acute ; volutions nine, 

 convex, longitudinally costate, and finely striated transversely ; ribs distant, promi- 



