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FROM THE TERTIARY OF VIRGINIA. 247 
Shell—, eight-valved? thick, costate, very much elevated and angular in the back; central area of the intermediate 
valves with straight, longitudinal, noduliferous ribs, lateral area smooth or nodulose; central area of the terminal 
valve nodulosely costate, lateral area nodulose. 
Length of valve .15. Breadth do. .50 of an inch. 
Remarks.—The ribs of the central area are perfectly parallel, sometimes nearly smooth, 
and sometimes armed with large nodules in regular series, giving them the appear- 
ance of being transversely sulcate. The lateral area, in most of my specimens, is 
smooth, with the exception of two or three impressed lines of growth, but on some there 
are numerous spherical tubercles, placed without any apparent order. As these are 
easily removed, I think it probable that all have been furnished with them, but that, in 
general, they have been obliterated by attrition. They bear some resemblance to the 
remains of spines. 
This well marked species differs in its sculpture and angulated back from all its 
congeners. 
This shell is interesting as being the first of its genus found in a fossil state in this 
country. I believe that but one, the C. Grignonensis, Lam., has been described from the 
Tertiary of Hurope. 
The third figure is a terminal valve, most probably from a young specimen. 
GENUS PATELLA. 
P. actnaces, Px. 35. Fic. 36. 
P. testé ovatd, valdé compressa, falcata, depressd, crassd, striis concentricis parvis; lineis radiantibus postice 
quatuor ; aperturd lineari; apice angulato, recto. 
Shell ovate, very much compressed, faleate, depressed, thick, with small concentric strie, and four radiating lines 
posteriorly, mouth linear; apex angular, straight. 
Height .15, Length .55. Breadth .10 of an inch. 
Remarks.—The apex is bent forward a little, and somewhat rounded. Diverging from 
it posteriorly are four elevated lines, two on each side, which may be traced to the base. 
The aperture is very narrow, almost acute anteriorly and rounded posteriorly. The 
substance of the shell is extremely thick, particularly at the apex. 
It is not without some hesitation that I have classed this little shell with the genus 
Patella. Its falcate, compressed shape appears hardly to belong to that genus, and yet 
is not sufficient to found a new one on. If, however, on farther examination, it should 
prove distinct, I propose the name of Scaphidium* for it, from its peculiar canoe-like 
shape. 
FAMILY CALYPTRAIDA, 
GENUS CEMORIA (Leacn.) 
C. optonea, Pi. 35. Fie. 37. 
C, testa conicd, sub-elevatd, tenui, diaphand, costatd; costis longitudinalibus, noduliferis, alternantibus ; apice pro- 
ducto, mecurvo, anfractu uno, sinistrorsum deflecto, levi; Soramine elliptico; apertura quadraté, oblonga. 
* A Sxopediov, navigiolum. 
