204 PALAEONTOLOGY OF KENTUCKY. 



Var. uttenuatum, Conrad, which are apparently only the young of C. 

 cuneus. 



Var. trigonale, the forms found in our rocks, and formerly always known 

 under that name. 



Var. nasutum, Hall, a short, very ventricose, and abruptly truncated form. 



Formation and Locality. This shell is not rare in our Devonian rocks, at and around the Falls ot 

 the Ohio, where it is often found in the rotten hornstone; but fair or perfect shells are not often met with. 

 1 have figured on plate 5 a small individual which comes as near perfection as possible; it shows the 

 whole shell with complete shield, and is a most beautiful but delicate fossil. I found it on the Indiana 

 shore of the Ohio, opposite the falls. 



Genus Cypricardinia. Han. 



Cypricardinia, Hall. Pal. N. Y., Vol. 3, page 2661859. 

 Etymology Resembling Cypricardia. 



Shell being inequilateral, with a more or less distinctly defined oblique pos- 

 terior ridge, the umbones anterior or sub-anterior, and little elevated. The 

 surface is concentrically grooved, or more or less distinctly marked by promi- 

 nent ridges or imbricating lamellae, and, on some of them, these lamellae are 

 radiatingly striated or cancellated. 



A single well-preserved specimen shows no external ligamental area. In 

 some species the posterio-cardinal margin becomes alate or sub-alate. They 

 bear some general resemblance to Modiolopsis, but the shell is apparently 

 thicker, and is more strongly marked by concentric striae, and with a less 

 conspicuous anterior muscular prominence, while the aspect and general ex- 

 pression of the shells are quite distinct. 



Cypricardinia cataracta. CONRAD. 



Plate IV., figure 3. 



The illustration of this species was made from the only specimen which I 

 then possessed ; that shell was defective in several places of its margins, in 

 consequence of which the figure does not show the exact shape or form of the 

 perfect shell. I shall try to correct this in my description. 



Shell of medium size, sub-rhomboid-ovate ; length one-half greater than 

 height ; basal margin nearly straight, slightly concave anterior to the middle. 

 Posterior extremity abruptly rounded below, and obliquely truncate above. 

 Cardinal line straight, oblique. Anterior end very short, rounded below. Both 

 valves about equally convex; the right one, apparently, little more than the 

 left. The left valve is somewhat compressed in its middle portion near the 

 basal margin, but it becomes very convex, almost gibbous, in its umbonal 

 region. 



