1863. | On Dr. Gerard’s collection of Spiti fossils. 131 
11. AMMONITHS SPITIENSIS, N. 8., Plate II. figs. 4, 4a, 40. 
Diameter of shell, 2 inches 38 lines. 
1. of outer whorl, 9 
Thickness, Lbous 
Width of outer whorl = 33, of the diameter of the shell. 
This Ammonite bears some resemblance to the 4. planula of 
29 
D’Orbigny, but is distinguished by the following characters -—the 
whorls of the Spiti species are somewhat narrower, the ribs more 
flexuous, and arcuated towards the front instead of towards the rear 
in the ventral area, and the shell is crossed at intervals of rather 
more than half a whorl, by deep oblique sulcations bounded poste- 
riorly by strong ribs. The sutures are identical with those of the 
A. planula, except that the ventral and superior lateral lobes of the 
Spiti fossil are equal in length, and it has but two minute accessory 
lobes, instead of 3, as figured by M. D’Orbigny. 
12. AMMONITES GUTTATUS, Strachey, Plate IV. figs. 1, la, 16. 
A testa discoidea, compressa. Anfractibus rotundatis, apud umbi- 
licum crassioribus, tuberculato-costatis, 3 sulcis obliquis notatis. 
Costis numerosis, tenuibus, apud umbilicum 3, 4-fasciatis, apud ven- 
ter, leniter anticé arcuatis. Ventre rotundato. Umbilico profundo, 
lato, tuberculis 20 coronato. Apertura semilunari? Septorum lobis 
lateralibus 6. 
Diameter of shell, 2 inches 1 line. 
» of outer whorl, 91, 
Thickness, Jac 
Width of outer whorl = 33, of the diameter of the shell. 
Very closely allied to the preceding species, from which it is 
distinguished chiefly by the characters of its sutures; the lobes 
and saddles being 4 longer, and the saddles narrower than in 
A. Spitiensis; while there are 4 conspicuous and 2 minute lateral 
lobes instead of 3 of the former, as in the above species. There 
are also some differences in the ornamentation, but how far 
these are constant Iam unable to say. Thus, in 4. Spitiensis, the 
ribs and tubercles are less numerous than in A. guttatus, and the sul- 
ei of growth are three to each whorl, and continuous in the former 
species, while in the latter there are barely 2 to the whorl. These 
latter differences I consider, however, to be unimportant, and should 
further specimens shew the sutures to be more variable than is usual 
8 
