DESCRIPTION OF THE FOSSILS. 
101 
This species is usually found in thin, more or less continuous, layers, adhering to the surface 
of calcareous laminae, which are largely composed of fibrous calcareous matter, similar to the 
outer part of the shell of Inoceramus, mingled with fragments of other shells. Sometimes 
laminae of this fibrous calcareous mass, several inches square, are entirely covered with this 
oyster adhering to one side. In other instances the fibrous laminae fill interstices between the 
shells, and radiate from different centres, as if having filled the space subsequent to the growth 
of the shells. 
Locality. —Brought by Mr. Marcou from three miles north. of Gfalisteo ; from the cretaceous 
marls on the Missouri by J. N. Nicollet; and by Mr. Meet and Dr. Hayden from the lower 
beds of the cretaceous rocks on the Missouri river, twenty-six miles above the mouth of l’Eau 
qui Court. 
CARBONIFEROUS SPECIES.- 
TEREBRATULA, Shwyd. TEREBRATULA MILLEPUNCTATA, n. sp.—Plate II, figs. 1, 2. 
Shell elongate ; curved from beak to base, dorsal (ventral) valve, with a broad mesial depres¬ 
sion, extending the entire length of the shell, obtusely subangular at the sides, which project 
beyond the margin of the opposite valve ; ventral (dorsal) valve varying from flat to extremely 
convex or gibbous along the line from beak to base ; surface minutely but conspicuously 
punctate. 
The specimen in the collection is imperfect, the beak of the larger valve being broken off. 
The smaller valve is slightly concave, in a longitudinal direction, and somewhat semi- 
cylindrical. 
Other specimens from Topeka, in Kansas, are extremely gibbous on the middle of the smaller 
valve ; while the larger valve is extremely arcuate, and the beak abruptly incurved with a per¬ 
foration above the apex. The Topeka specimens are less elongate than the one here described. 
Locality. —Pecos village (New Mexico) associated with T. subtilita, and Spirifer cameratus, 
and S. lineatus. 
TEREBRATULA SUBTILITA.—Plate II, figs. 3, 4, 5. 
Terebratula subtilita, Hall; Stansbury’s Report, page 409, plate IY, figs. 1 and 2. 
Gibbous, obovoid, valves nearly equally convex ; beak of dorsal valve elevated, incurved, and 
perforated at the apex ; a mesial depression commencing just below the centre and extending to 
the front, which is produced and elevated, filling a broad sinus in the ventral valve ; surface 
marked by strong concentric lines of growth, with faint, almost imperceptible, radiating striae. 
There are a large number of specimens of young and full grown individuals, exhibiting a 
great variety of form. In many instances the mesial depression is not fully developed until the 
individual is more than half grown ; but sometimes it is well exhibited in the young shell. 
Several of the specimens show a narrow, sharply impressed line along the mesial depression 
from the beak to the base of the dorsal valve. 
Locality. —Pecos village, near Santa Fe, New Mexico, where it occurs in abundance, associ¬ 
ated with Productus and Spirifer cameratus. 
It was also found on the Missouri river, near Weston ; and is known in numerous localities 
in the west. 
SPIRIFER, Sowerby. SPIRIFER LINEATUS.—Plate II, figs 6, 7, 8. 
Anomites lineatus, Martin. 
Spirifer lineatus, De Koninck, De Verneuil, and other authors. 
Shell inflated subglobose ; sometimes transverse and subelliptic; dorsal valve scarcely more 
convex than the ventral valve; mesial line marked by a scarcely perceptible impressed line 
which sometimes becomes developed in a shallow sinus in front; umbo prominent, beak incurved, 
area short, extremities rounded; surface marked by fine concentric laminae which are crossed 
by longitudinal striae. 
