266 
PALEONTOLOGY OF NEW-YORK. 
which they may be separated from the Swedish specimens. In well preserved specimens from 
Gothland, the striae are sharp, or round and prominent, and crossed by conspicuous elevated 
concentric striae, which, towards the margin, are undulated upon the elevations and depressions 
of the plications. All the New-York specimens I have seen are destitute of the concentric striae, 
and the longitudinal striae are often flattened. This character, however, may arise from abra¬ 
sion or partial exfoliation ; and, in the shale, the presence of iron pyrites, producing solution 
of the surface by sulphuric acid, is a probable cause of the absence of the more minute surface 
markings. 
It is not a little interesting to the palaeontologist and zoologist to consider the fact, that 
while we have no evidence of a plicated surface in this species from the New-York (and pro¬ 
bably all American) strata, we yet have another species of similar form, and a similarly striated 
surface, which is distinctly plicated from beak to base, and never deviates even in the youngest 
specimens seen. This species (the S. niagarensis) appears to be unknown in Europe, where the 
other species is common. We can not avoid the thought that the manifestation of a peculiar 
feature in the S. radiatus of Europe was more strongly developed in a distinct, but allied form, 
in the western ocean, and which now appears as a characteristic species of the Niagara period. 
Fig. 6 a, b. Ventral and front view of a small specimen. 
Fig. 6 c. A large specimen entirely flattened, which causes the beak to project as shown in the 
figure. 
Fig. 6 d. A specimen from which the shell is partially exfoliated, showing the form of the mus¬ 
cular impression. 
Fig. 6 e. Cardinal view of the. same, showing the entire extent of the dorsal area and foramen, 
which is partially closed above, and broadly triangular. This feature is in remarkable 
contrast to many specimens in the Clinton group as shown on plate 22. 
Fig. 6 /. The interior of a dorsal valve, showing the extension of the plates or laminae on each 
side of the foramen, with a central one commencing below the beak. 
This character corresponds precisely with the S. niagarensis (see fig. 4 r), where 
the interior of a small dorsal valve is shown. This coincidence increases the interest 
in the similar external characters of the two species. 
Position and locality. This species is not common in the shale of the Niagara group, though 
occurring in many localities in the lower part of the same, associated with the preceding species. 
626. 9. SPIRIFER PYRAMIDALIS (n. sp.). 
Pl. LIV. Fig. 7 a-e. 
Compare Delthyris elevata, Dalman, Vet. Acad. Handl. 1827, pag. 120, t. iii, f. 3. 
Shell pyramidal; dorsal valve extremely elevated ; beak acute ; area vertical or slightly bent. 
forwards; foramen linear, filled by a projecting callosity; ventral valve semicircular, nearly 
flat, or convex only along the mesial fold ; surface plicated ; plications subangular, about five 
on each side of the mesial fold and sinus, crossed by fine threadlike striae. 
