7 O 
PALAEONTOLOGY OF NEW-YOKK. 
Notwithstanding these slight differences, I feel disposed to recognize the 
two as distinct; though, adopting the line of argument which has been used in 
regard to the Lower and Upper Helderberg Strophodontm*, I should be compelled 
to regard the S. pandora as identical with S. woolworthana. There will be found, 
moreover, among the species of several genera of the Brachiopoda from ihe Lower 
and Upper Helderberg formations, a like degree of similarity as I have already 
shown to exist between the Niagara and the Lower Helderberg species. 
The conditions prevailing during the epoch of the Upper Helderberg formation 
were very similar to those during the Lower Helderberg, the two being separated 
by the Oriskany sandstone and Cauda-galli grit. There was, during the older period, 
a greater amount of shaly matter deposited than during the later period, which is 
almost wholly calcareous, and we have in the entire fauna an adaptation to these 
conditions. 
The S. pandora first appears in the Schoharie grit, where it occurs in considerable numbers, 
although generally in the condition of casts. It has, in this part of the formation, attained a 
diameter of nearly two inches in some of the larger specimens. Figs. 11 - 19 of Plate iv 
represent its usual condition in this rock. Fig. 12 is drawn from a cast of a ventral valve, 
made in a natural mould in the stone. Figs. 11, 15 & 16 ar casts of the dorsal valve, while 
13 & 18 are casts of the ventral valve. Fig. 14 is an artificial mould of the interior, from a 
cast in stone, and does not fully represent the cardinal process. Fig. 19 represents a specimen 
with the sides more regularly curved than usual. 
The figures on Plate ix, from 18 to 25 inclusive, are of specimens from the Corniferous 
limestone; showing the dorsal, ventral, and profile views of a symmetrical specimen, with the 
interior of the two valves, hinge-line, etc. 
The figs. 19 - 23 of Plate x are illustrations of the casts of symmetrical forms from the 
Chemung group, and which differ in no essential degree from the S. pandora of the Corni¬ 
ferous limestone. 
The casts from the Schoharie grit show stronger muscular impressions, owing to the thicker 
shell; while the Chemung forms, having lived among sediments containing little calcareous 
matter, have had a thinner shell, and consequently the muscular imprints are less conspicuous 
in the cast. 
Geological formation and locality. In the Schoharie grit at Schoharie, Knox¬ 
ville, Clarksville and other places, and in the Corniferous limestone at Clarksville 
and Schoharie; at Eastman’s quarry south of Utica; in Ontario county, and at 
Clarence-hollow and Williamsville in Western New-York; and in Canada West; 
being coextensive with the Limestone formation in this State and Canada. 
Billings in Canadian Journal, July, 1861. 
