214 PALAEONTOLOGY OF KENTUCKY. 



Surface marked by more or less regular concentric striae, which may be either 

 simple throughout or fasciculate on the anterior portion of the shell. Some 

 species are marked by strong, radiating striae upon that portion of the valves 

 between the umbonal ridge and the sinus. 



Hinge furnished with a strong oblique fold or tooth in the left valve, situ- 

 ated just beneath the beak, and a corresponding depression in the right valve. 

 No lateral teeth have been observed. Ligament external, strong; its attach- 

 ment to the shell is marked by one or more defined grooves. Muscular im- 

 pressions two ; the anterior one deep and strongly marked, situated a little 

 anterior to the beak and just within the anterior margin. Pallial line simple, 

 continuing nearly parallel to the basal margin until it crosses the umbonal 

 ridge, and recurving to the posterior muscular impression, which is large arid 

 shallow, and situated on the posterior cardinal slope, sometimes near the mid- 

 dle of length of shell. 



This genus was proposed by Phillips in 1848, as a generic designation for 

 the original Cypricardia cymbiformis of Sowerby, but without generic defini- 

 tion or illustration of internal characters, and, so far as known, the genus 

 has never been heretofore described. 



Goniophora truncata. HALL. 



Plate IV., figures 21, 22 and 23. 



Goniophora truncata, Hall. Pal. N. Y., Vol. 5, pt. 1, pis. 1883. 

 Goniophora truncata, Hall. Pal. IS. Y., Vol. 5, pt. 1, p. 2981885. 



Shell of medium size, in a side and front view sub-triangular, in a dorsal 

 view sub- elliptical. Length about twice as great as height ; anterior end of 

 the basal margin rounded, middle portion slightly sinuate, and the rear por- 

 tion nearly straight or slightly curved to the post-basal extremity ; posterior 

 margin obliquely sub-truncate, slightly curving. Cardinal line short and 

 straight. Anterior end short and rounded. There is a broad, shallow de- 

 pression extending from the beaks obliquely across the valves to the central 

 point of the basal margin ; this last feature is only faintly expressed in some 

 specimens, and in others entirely obsolete. Valves convex below the umbonal 

 ridge, gibbous in umbonal region. The area above the umbonal ridge, which 

 I called [in Cypricardinia cataracta the dorsal incline, is usually flattened or 

 very slightly convex ; in some shells it is even concave. The beaks are entirely 

 anterior, acute and incurved ; in some shells they are closely appressed, while 

 in others they are separated by a small interspace. 



The umbonal ridge is strongly defined, forming a very sharp edge, separating 

 the lateral areas of the valves from their dorsal incline. Cardinal line is short 

 and straight, the umbones are more or less prominent and somewhat angular. 

 Test is of moderate thickness, the entire shell marked by stronger and finer 



