43 ® 
PALAEONTOLOGY OF NEW-YORK. 
In the sandstone of New-York the species is very rare, a single cast only having 
been seen in all the collections made. 
PLATE XCVI. 
Fig. 1 a, b. Dorsal and cardinal views of a young specimen, which has six plications on each 
side of the mesial fold. 
Fig. 2 a, b. Dorsal and front views of a larger specimen. 
Fig. 2 c, d. Profile and cardinal views of the same specimen. 
Fig. 3 a, b. Cardinal and front views of another individual, with a higher area and less ex¬ 
tended hinge-line. The beak in fig. 3 a, as represented, is not sufficiently elevated. 
Fig. 4 a. Ventral valve of an old specimen. 
Fig. 4 b. Dorsal valve of the same. 
Fig. 4 c, d. Profile and cardinal views of the same specimen. 
Fig. 5. Interior of the dorsal valve. 
Fig. 6 a, b. The exterior and interior of a dorsal valve of this species. 
PLATE XCVIII. 
Fig. 8 a, b. Ventral and cardinal view of an imperfect cast of this species. 
Geological position and locality. In the Oriskany sandstone : Albany county (New- 
York), and Cumberland ( Maryland ). 
The preceding species of Cijrtia is presented in so many varieties of 
form, and with such a degree of variation in the number of plications, 
that I had regarded the specimens figured as of two distinct species. A 
farther examination, however, with a larger number of specimens before 
me, has convinced me that these are all varieties of a single species. 
There is yet room for inquiry in regard to the degree of variation as¬ 
sumed by Spirifer arrcdus, or whether some of the forms occurring with 
this one are really varieties of it; or whether they may be a distinct 
species more nearly related to S. cyclopterus , or perhaps a variety of the 
latter species, which, in the sandstone, attains a larger size than in the 
shaly limestone below. 
The Spirifer intermedius has not been seen in specimens sufficiently 
well-preserved, to admit of the full determination of its more minute 
characters. 
