1863. | On Dr. Gerard’s collection of Spiti fossils. 127 
planato, costato. Umbilico angusto; lateribus leniter inclinatis, ro- 
tundatis. 
Diameter of shell 2 inches 1 line. 
wr omouver whorl Lio’ jy. 22s, 
Thickness Play 
Width of outer whorl = ;°5 of the diameter of the shell. 
A peculiar form, combining the characters of the Globosi and 
Amalthet groups. The young shell is smooth, (in the single speci- 
men described, to beyond the commencement of the body chamber,) 
and the last half whorl ornamented with strong, simple compressed 
ribs, inclined forwards from the umbilicus, and becoming more ele- 
vated as they approach the ventral region, on the sides of which, 
they rise almost into tubercles; then becoming less prominent as 
they bend forward on each side of the median line, they form an an- 
gle in the centre, being again elevated at the bend into a series of 
flattened tubercles. The whorls are rounded in the young, squared 
in the old shell. The sutures are very imperfectly seen: the saddles 
appear to be squared in form, and symmetrically divided, and the 
superior lateral lobe is probably longer than the ventral as in the 
Globosi. 
4, AMMONITES WaLuicut, Gray, Plate I. figs. 4, 4a, Plate III, 
figs. 2, 3. 
A. testa discoidea, compressa, transversim costata. Anfractibus 
subcompressis, complanatis. Ventre angusto, excavato, levigato. Cos- 
tis acutis, bifurcatis, haud tuberculatis. Umbilico lato, profundo. 
Apertura oblongo-quadrata. Septis, lateraliter 5-lobatis. 
Diameter of shell 1 inch 9 lines. 
» of outer whorl 73 ,, 
Thickness TPs 
Width of outer whorl = 23, of the diameter of the shell. 
This ammonite, of which there are two specimens in the collection, 
is allied to A. Parkinsoni, Sowerby. The chief points of departure 
from the latter species are;—the absence of tubercles; the greater 
width of its whorls (33, instead of 2,4, of the diameter) ; and some 
differences in the sutural lobes, the superior lateral being barely so 
long as the ventral lobe, and having fewer ramifications than that 
of A. Parkinsont. The two specimens before me differ somewhat 
