80 
JURASSIC, OR 
nodules. I can detect no difference between them and the 
characteristic Oxford clay specimens of Europe. They are 
identical also in all respects (mineral character included) with 
those from Spiti, lately described by myself, from Dr. Gerard's 
collection. 
AMMONITES TRIPLICATUS.—Swerty. 
Plate 13, figs. 1 a-c. 
A. triplicate, Sow., Min. Concli., Plate 292 and 293, f. 3, 4. 
This Ammonite is only distinguished from the preceding 
by the fasciculate character of the ribs in adult specimens, 
young shells of the two species being undistinguishable. It 
is, however, the case with many allied species of Ammonites, 
as has been pointed out by M. D'Orbigny, that the specific 
characters of ornament are only assumed by the adult shell, 
and I follow, therefore, the majority of English authors in 
treating provisionally the two forms (with bifid and fascicu¬ 
late ribs respectively) as distinct. 
AMMONITES TORQUATUS- 
A. torquatus, Sow., Trans. Geol. Soc., 2nd Ser., vol. v., pi. 21. 
A. torquatus Blanf. Spiti fossils, in Journ. As. Soc., Bengal. 
The only characters by which I can distinguish this species 
from A. bipletc, Sow., are :—Its thicker and more depressed 
whorls, and a slight notching of the ribs above the siphuncle. 
These characters are exhibited by the typical Cutch specimens, 
as well as by those in Colonel Strachey's cabinet,* and also 
by the specimens described and figured by me, in the 
Spiti collection of Dr. Gerard. The distinctness of the • 
notching and the depression of the whorls vary, however, in 
different specimens, and a more extensive comparison is 
* All the figured specimens of Colonel Strachey’s collection have been 
liberally presented by that gentleman to the Museum of Practical Geology, 
London.—J. W. S. 
