410 
PALEONTOLOGY OF NEW YORK. 
obliterates the radii. At the junction of these thickened portions, along the 
base of the valves, the shell is excavated, leaving a tubular opening extend¬ 
ing backward from the post-inferior extremity, as shown in figs. 27, 29 and 
52 of plate lxvii, and more fully in fig. 12 of plate xciv. 
Valves crenulated along their margins. Anterior muscular impressions 
elongate, deeply impressed, narrower behind. 
Four specimens measure respectively 60, 47, 43 and 21 mm. in length, 
and 30, 33, 26 and 13 mm. in height. 
This species resembles C. Jiormale, in the Hamilton group, but that form is 
usually more elongate with uniform simple ribs, and the interradial spaces are 
marked by fine radiating striae. 
The specimens here referred to a single species are subject to great variation 
in form and general aspect. The main differences are indicated in the follow¬ 
ing varietal designations : 
Var. attenuatum, Conrad. PI. 67, figs. 1-11. The specimens referred to this 
form are apparently the young of C. cuneus, preserving numerous uniform, 
fine radii upon the surface and the posterior extremity not abruptly 
truncated. Specimens having these characters, as they become larger, 
show a duplication of the radii and gradually assume the character of 
C. cuneus. 
Var. trigonale , Hall. PI. 67, fig. 28; pi. 68, figs. 1, 4-16; pi. 94, fig. 11. 
This name is given to the specimens occurring in the Corniferous limestone 
and originally described as a distinct species. 
Var. nasutum , Hall. PI. 67, figs. 12-20. This name is applied to short, 
triangular forms, which are broad and abruptly truncated behind, abruptly 
contracted in front, with the anterior end nasute. The body of the shell 
is marked by fewer radii than in characteristic forms of C. cuneus. 
Formations and localities. In the Schoharie grit, at Schoharie, and the Hel- 
derberg mountains, and on the outcrop of the same formation in the neighbor¬ 
hood of Rondout, Ulster county, and in Orange county, N. Y.; in the Cornif¬ 
erous limestone, at Williamsville, N. Y.; at Dublin and Columbus, Ohio; and 
at the falls of the Ohio river. It also occurs at Cayuga and other places in 
Canada West. 
The species, in its varieties of form, occurs at Pendleton, Indiana, in a sand¬ 
stone which probably represents the horizon of the Schoharie grit. 
