SPlRIFERiE OF THE CHEMUNG GROUP. 
249 
the opposite valve. The casts of the dorsal valve show the marks of a 
deeply striated cardinal process and elongate teeth-sockets, while the 
muscular impressions are sometimes strongly marked. 
This species is known to me only in the condition of casts of the interior, and 
its usual appearance is illustrated in the figures on Plate XLin. Its general aspect 
is much like that of the European Spirifera cuspidata, Martin; but there are 
important differences by which it may be distinguished : these are, the plications 
on the mesial fold, the larger area of the dorsal valve, and the shorter extension 
and greater divergence of the dental lamella} by the sides of the muscular im¬ 
pression. Some of these characters, I conceive, are not likely to change to those 
shown by 8. cuspidata. In the concave septum closing two-thirds of the fissure 
from above, it resembles that species as described by Prof. M‘Coy, who mentions 
the presence of a “ deep-seated pseudo-deltidium.”* In one of the figures given by 
Mr. Davidson and referred with doubt to this speciesf, the cast shows a tubular 
perforation in the filling of the fissure; and a gutta percha impression from the 
same shows the mark of a foramen, but there is no positive evidence of a septum 
which is so conspicuous in our specimens, and which I suppose to be the feature 
characterized by Prof. M‘Coy as a deep-seated pseudo-deltidium. In our species, I 
have not been able to discover any corresponding perforation; the only indication 
of this being the semicylindrical impression along the centre of the fissure (in the 
cast), showing a callosity of the septum behind the exterior wall. 
In form and proportions, this species bears a very close resemblance to one in 
the Waverly sandstone of Ohio, and also to one in the fine-grained sandstone of 
Burlington, Iowa; but of neither of these have I the necessary material for satis¬ 
factory comparison. It differs from the S. subcmpidata% of Schnur in the plications 
on the mesial fold and sinus, and the wider area of the dorsal valve; and also in 
the same characters it differs from the 8. textns of the sandstone and argillaceous 
limestone near New-Alb any, Indiana. 
Geological formation and locality. This fossil occurs in finegrained ferruginous 
sandstone of the Chemung group, at Meadville, Pennsylvania; associated with 
Spirifera disjuncta , 8. prcematura, 8treptorhynchus chemungensis var. pectinacea, 
Chonctes muricata , C. 9, Productus (Productella ) lachrymosa , etc. 
* * * * *. triangular opening very large, often displaying the internal deep-seated pseudo- 
deltidium (without perforation, leaving the only opening to the shell at its base); * * *. McCoy, 
British Palaeozoic Fossils, p. 426. 
t Monograph of British Carboniferous Brachiopoda, Plate ix, f. 1 & 1 a. 
t Spirifer subcuspidatus, Hall, Geological Report of Iowa, pa. 646, pi. 20, f. 6, is a distinct species, 
and apparently identical with S.-textus, Hall, Tenth Report on the State Cabinet, p. 160 : 1857. See 
Nineteenth Report on the State Cabinet, for remarks on this, species. 
[Paleontology IV.] 32 
