132 On Dr. Gerard’s collection of Spiti fossils. [No. 2, 
in Ammonites of the same group, there would remain no good reason 
for distinguishing the two forms in question. 
13. Ammonires Hypnasis, n.s. Plate IV. figs. 2, 2a, 26. 
A. testa discoidea, compressa, costaté. Anfractibus subquadratis, 
parum amplexantibus. Costis valdis, rectis; nonnulis (plerumque 
alternantibus) bifurcatis; medio ventre parum incisis, haud inter- 
ruptis. Ventre planato. Umbilico magno: suturis impressis. Aper- 
tura reniformi. Septorum lobis lateralibus 4. 
Diameter of shell, 1 inch 10 lines. 
* of outer whorl, Uae 
Thickness, 84,5 
Width of outer whorl = ,3), of the diameter of the shell. 
Intermediate in form between A. communis, and A. Parkinsoni, this 
shell is distinguished from the first by the mesial notching of the ribs 
which indicates an approach to the Dentati, (Ornati of Von Buch) ; 
and from the second by its continuous ribs, as well as by the inferior 
number of its lobes and their greater equality in size. Some of the 
ribs carry a small tubercle at the bifurcation, which occurs alternately 
on the opposite sides of the whorl. The collection contains two small 
specimens of this Ammonite, which are precisely similar to each 
other, and a fragment of a larger specimen 12 inches in thickness. 
14, Ammonites GERARDI, n.s. Plate II. figs. 6, 6a, 60. 
A. testé subglobosa, levigata, angusté umbilicataé. Anfractibus 
ventraliter subcompressis, amplexantibus ; senioribus, radiatim laté 
undulatis. Ventre rotundato. Umbilico parvo, profundo. Apertu- 
ra trigona, apud dorsum valde excavata. 
a b 
Diameter of shell 2 inches. 3+ inches. 
Fe of outer whorl 1 inch. ee 
Thickness es 2 lines. 14 
Width of outer whorl = 55°, of the diameter of the aie 
This Ammonite belongs to a group largely represented in the 
Triassic beds of St. Cassian, and of which one species only, A. ster- 
nalis, Von Buch, is described by M. D’Orbigny, Quensted and others 
from the Upper Lias of France and Germany.* ‘To this species, A. 
Gerardi bears much external resemblance, but the sutural ramifica- 
tions of the Spiti fossil prove it to be without doubt a distinct spe- 
* Several species occur in the Cretaceous rocks of S. India. 
