58 
PROCEEDINGS OF THE ACADEMY OF 
from three to six sharp digitations. The next succeeding lobe is not more than 
one-fourth as large as the superior lateral lobe ; it is, on one side of the shell, 
divided nearly to its base, into two equal branches ; while the corresponding lobe 
on the other side, is narrower, and rather regularly divided into three short 
sharply digitate branches. The remaining lobes are very small, and simply 
digitate at their extremities. Greatest diameter 2-14 inches ; transverse diameter 
1-33 inches. 
This species is remarkably distinct in its internal structure from all the Am- 
monites hitherto found in this country. We take pleasure in naming it in honor 
of the distinguished philosopher Prof. Joseph Henry, Secretary of the Smith- 
sonian Institution. 
Locality and position. Southwest part of Black Hills, lower bed of No. 1, gene- 
ral section of Nebraska formations, and of preceding section. 
SCAPHITES LARV^FORMIS. 
Shell small, ovate, laterally compressed, rounded on the dorsum; body whorl 
cylindrical, first extended horizontally from the convoluted inner whorls, then 
curving upwards a little, after which it bends backwards upon itself, so as to 
bring the aperture almost in contact with the inner coil; but leaving a free space 
within the curve. Inner whorls mostly hidden, forming a small coil at one end 
of the shell, and so closely rolled up as to leave but a very small umbilical im- 
pression : aperture nearly circular. Surface ornamented by rather small costae 
which pass round a little obliquely from the inner side of the whorls, to a point 
about halfway across the outsides, where they swell out into small obscure 
transversely elongated nodes, and then each branch into two or three smaller 
costse, which pass very regularly over the dorsum. 
The septa are moderately close, and provided with three lobes on each side, 
of which the superior lateral is the largest. The dorsal lobe is still larger, 
and provided with two small obscurely bilobale branches on each side. Greatest 
length .88 inch.; greatest height -60 inch ; breadth of the body whorl -32 inch. 
This species is very closely allied in the structure of its septa to S. hippocrepis^ 
DeKay, {S. Ciivieri, Morton, Synop. Org. Remains, pi. vii. fig. 1,) but differs 
in the details of its septa lobes, and the body whorl is proportionally much more 
slender, more cylindrical, and forms a larger curve ; it also wants the outer row 
of round nodes. 
Locality and position. — East base of the Black Hills, formation No. 2 of the 
general section. 
Belemnites census. 
Shell large and thick, subcylindrical, more or less compressed laterally, so as 
to give tlie cross section a slightly oval outline: lower portion tapering to a 
point, sometimes a little oblique, usually more compressed than any part above, 
often having a narrow obscure groove on the ventral side, and sometimes a very 
slight carina on the dorsal side, near the apex ; the groove being more frequently 
present than the carina, and extending further up from the point: surface 
smooth. 
Alveolus extending about half way down from the summit to the lower ex- 
tremity, where it terminates nearly midway between the centre and the ventral 
side ; from this point the apical line passes down, gradually approaching the 
ventral margin, but curving slightly so as not to intersect it before reaching the 
apex. 
Phragmacone conical, very slightly curved, apical angle 20° ; septa rather 
closely arranged, about twenty of them occurring in a section one inch in length, 
measuring -72 inch in diameter at the larger end, and .35 inch at the smaller 
end I siphuncle unknown. 
The best specimen we have seen, of the outer horny shell, measures 5 inches 
in length, and -90 inches in diameter at the larger end ; the alveolus measures 
[March, 
