i m 
PALEONTOLOGY OP NEW-YORK. 
The illustrations on Plate XXIII, figures 18, 19 & 20 are enlarged three diameters, and 
those from 12-17 are enlarged two diameters. The interior of the dorsal valve show¬ 
ing the cardinal process, is enlarged sis diameters. 
Figure 28 represents the impression left in the stone by a dorsal valve, with the area 
and minute foramen of the ventral valve. This one is a little less broadly truncate, 
and presents other slight differences from the ordinary forms of this species. 
Geological formation and localities. This specie's occurs principally in the calca¬ 
reous beds of the Marcellus shale, and in the shale itself. It is found in large num-' 
bers near Schoharie, and also near Manlius in Onondaga county, at Avon in Liv¬ 
ingston county, and on the shore of Lake Erie above Buffalo. It occurs also in the 
shale of the Hamilton group near Tully in Onondaga county. 
Prodiictella duinosa. 
PLATE XXIII. 
Productus dumosus : Hall, Fourteenth Report on the State Cabinet, p. 99. 1861. 
Compare Productus spinulicosta : Hall in Tenth Report on-the State Cabinet, p. 173. 1857. 
Compare Productus shumardianusi : Geol, Report of Iowa, Yol. i, part ii, pa. 499, pi. 3, f. 9, and pi. 7 
f. 1; and this volume p. 150. 
Body of the shell subovate, and, including the ears, somewhat hemi¬ 
spheric ; length and width about equal; the hinge-line usually a little 
less than the greatest width of the shell. 
Ventral valve extremely gibbous or ventricose in the middle, contracted 
at the umbo, which is prominent, with the beak strongly incurved 
over the hinge-line. The middle and lower part of the shell is regu¬ 
larly arching, and almost vertically depressed at the sides of the umbo 
to the narrow flat ears. Dorsal valve more or less deeply concave, cor¬ 
responding nearly with the opposite valve. 
The surface of the ventral valve is marked by numerous slender spines, 
the bases only of which are usually preserved. The spines on the umbo, 
and a row on the ears, rise almost vertically from the surface; while 
below this the surface is marked by short rounded ridges, each of 
which terminates in a slender spine. Towards the front of the shell 
the ridges are continuous, being only slightly interrupted by the 
growth of the spines. The bases of the spines are more or less distinctly 
arranged in concentric rows, and vary greatly in their number and 
proximity to each other. The entire surface is marked by closely 
