ORISKANY KAtJNA OF BECRAFT MOUNTAIN 37 



Conocardium inceptum Hall (?) 



Plate 4, fig. 21-23 



1857. Conocardium inceptum Hall, Paleontology of New York. 3 : 491 



Shell small, obliquely triangular, anterior slope abrupt, posterior 

 surface moderately extended. The heart-shaped anterior surface is some- 

 what convex at first but becomes depressed nearer the margin. The 

 median portion of the valves is prominent, somewhat oblique anteriorly, 

 and its crest is ridged by the remnant of the anterior expansion. The 

 posterior is concave medially, the extremities of the valves being turned 

 upward. 



External surface marked by fine, sharply elevated radial plications 

 in a primary and secondary series, the members of each being of about 

 equal size. These are crossed by finer, concentric erect lamellae making 

 a deep cancelation of the exterior. On internal casts the surface appears 

 to bear libs of which five or six in the posterior region are broad and 

 separated by narrow furrows; over the middle of the valves the ribs are 

 much narrower, eight or 10 in number, and the intervening furrows are 

 broad, sometimes showing traces of intercalary ribs in each. On the 

 posterior slope the ribs become broader again. 



The original description was based on very incomplete material, 

 unaccompanied by figures. So far as can be ascertained the Oriskany 

 shell is identical with this Helderbergian species. The aspect of 

 the plication in internal casts is not unlike that of some of the small 

 examples of Conocar. cuneus var. n a s u t u m Hall, of the 

 Schoharie grit 1 and particularly that of Conocar. concinnum Hall 

 of the Hamilton shales 8 to which it corresponds in size, but we are 

 not yet fully acquainted with the exterior of these shells. Average 

 length and width of shell, 10 mm. 



l See Paleontology of New York. v. 5, pt 1, pi. 67, fig. 13. 

 "PL 68, fig. 26, 27. 



