130 On Dr. Gerard's collection of Spiti fossils. [No. 2, 
mens of this species, and indeed of many of the Planulatz and some 
other Ammonites, is that the last two or three sutures are frequently 
closer than the preceding, and are more or less shortened and dis- 
torted. In order, therefore, to establish a reliable comparison, and to 
avoid erroneous specific distinctions, one of the older sutures should 
be regarded as the standard. I give an illustration of this in figs. 
4b and 4c of Plate III. the first of which represents the last suture 
of the whorl, (that terminating the body chamber,) the second, the 
sixth suture of the same specimen, counted backwards. I have ob- 
served similar irregularities in A. inflatus, and many Nautili (e. g. 
NV. Bouchardianus,) have the last one or two chambers considerably 
narrower than those formed during earlier growth. 
Fig. 5, Plate III. is the last suture of a specimen of the normal 
variety of A. beplex, which I give as it is the only one visible on any 
of my specimens. 
9. AMMONITES TRIPLICATUS, Sowerby. 
Two specimens differ from the preceding in having the ribs, es- 
pecially those of the last whorl, trifureate. I have seen specimens 
both from Niti and Spiti with fasciate ribs, but otherwise undistin- 
guishable from A. biplex. I am inclined to doubt whether they be 
other than varieties of that species. 
10. AMMONITES TORQUATUS, Sow.? PI. III. figs. 6, 6a, 7, 7a, 8. 
A. testa, discoidea, compressa, costata, laté umbilicaté. Anfracti- 
bus rotundatis, depressis, convolutis. Costis filiformibus, rectis, anticé 
inclinatis, apud 2 anfractuum diametris bifurcatis. Ventre laté ro- 
tundato, costato. Apertura reniformi. Septorum lobis lateralibus 4. 
a b 
Diameter of shell, 1 inch 6 lines. 
m of outer whorl, Dias 9 lines. 
Thickness 7%, ineh 12 
9? 
Width of outer whorl = ,28, to 32, of the diameter of the shell. 
This shell is distinguished from A. beplex chiefly by its depressed 
whorls, and also by the greater width and comparative shortness of 
the saddles and lobes. ‘The ornamentation of the shell is precisely 
that of A, biplew, and it is indeed possible that A. torguatus may be 
merely a variety of that species, but until specimens of intermediate 
form, &c., have been discovered, the distinctions I have indicated are 
too considerable to be disregarded. 
