ISO 
PALEONTOLOGY OF NEW-YORK. 
The muscular impressions consist of a narrow central scar just below 
the apex of the beak, for the occlusor muscles, with a central elongate 
oval scar marking the place of the divaricator muscles; while there are 
two elongate ovate or pyriform scars, one on each side of the apex, and 
spreading laterally just within the limit of the constricted line, figure 7/. 
The figures 7 a-f illustrate the usual form and convexity of the species. The character of 
the cast of the ventral valve is shown in figures 7 e,f, where the marks of the internal 
tubes of the area are conspicuous. 
The cardinal spines are rarely visible, owing to the incurved margin which usually leaves 
these appendages imbedded in the stone. In one specimen, however, five or six spines 
are seen on one side of the apex. The shell of the area is penetrated from the interior 
by numerous comparatively large cylindrical tubes, some of which terminate in elon¬ 
gate spines upon the exterior margin. In one specimen, fifteen of these tubes may be 
counted on one side of the apex. In the casts or partial casts of the shell, these tubes 
give the appearance of coarse crenulations. 
This species is distinguished from C. hemispherica by being a little less promi¬ 
nent on the umbo, and by the shallow sinus, as well as the more numerous and 
much finer strise. The cast does not preserve the marks of the striae so conspicu¬ 
ously, while the surface is more abundantly pitted, without being sensibly 
arranged in distinct lines. 
Geological formation and locality. This species has been found only in the Cor- 
niferous limestone, near Williamsville and Clarence-hollow in Erie county, N. Y. 
Clionetes acutiradiata. 
PLATE XX. 
Strophomena acutiradiata : Hall, Geol. Report 4th District New York, p. 171. 1843. 
Chonetes acutiradiata : Hall in Tenth Report on the State Cabinet, p. 117. 1857. 
Shell nearly semicircular, sometimes a little more than twice as wide 
as long; the cardinal extremities produced. 
Ventral valve moderately convex, sometimes a little gibbous in the 
upper part, and frequently flattened or depressed at and below the 
middle : umbo little elevated above the hinge-line; greatest convexity 
above the middle, from whence it curves gently to the front, somewhat 
abruptly depressed towards the cardinal extremities, which are subau- 
riculate and nearly flat. In two individuals, there is a distinct longi¬ 
tudinal sinus in the middle of the valve. 
