280 
NAUTILOIDEA. 
chamber, in a specimen (No. 88590 h) having a maximum diameter 
of 1 foot 3 inches. Sutures nearly straight on the sides of the 
shell, and slightly emarginate on the periphery. The siphuncle in 
a young individual (No. 36603), 1| inches in length, is very near 
the inner (dorsal) margin of the septa, where also there is a very 
conspicuous lobe in the sutures. Test unknown. Casts show that 
when the shell attained a diameter of 5 inches, strong T-shaped 
ribs were developed upon the periphery. These ribs are about 
3 lines wide, with narrow interspaces, and are bent backwards at 
an angle of about 130 degrees. They cease to be visible when the 
shell has increased to a diameter of 7 inches ; but on reaching what 
is probably the adult stage of growth, the cast exhibits on the body- 
chamber very faint indications of what may have been either fine 
ribs or coarse lines of growth. Length of the body-chamber rather 
less than half that of the last whorl ; the aperture slightly con- 
stricted close to the edge. 
In the cast (No. 37901, fig. 62 h) the ribs are about 3 lines wide, 
with narrow interspaces about half the width of the ribs (?). 
RemarJcs. A species possessing somewhat similar sculpture is 
described by H. F. Blanford from the Cretaceous rocks of Southern 
India under the name of Nautilus rota. In this species the ribs 
“ are generally more strongly marked on, and quite close to, the 
outer [peripheral] region, and also usually round the umbilicus 
N. rota may easily be distinguished from the present species by its 
more compressed form and strongly bent sutures 
Horizon. Upper Grreensaud. 
Localities. Devizes, Wiltshire ; Swanage, Dorsetshire. 
Nautilus ventroplicatus, Foord. 
Sp. Char. Shell somewhat inflated, rather compressed on the 
sides, broadly rounded on the periphery. Umbilicus small, with 
rounded margin and rather steep sides. Greatest width of the shell 
in the umbilical region. Septa somewhat distant from each other ; 
the sutures slightly curved on the sides of the shell. Ornaments 
consisting of strong rounded ribs developed only in the peripheral 
region, where they form a backwardly directed sinus. On a cast 
(No. 88590 c) in which part of the test is preserved, about three of 
the ribs, including the narrow interspaces, occupy a space of 5 lines. 
^ Mem. Geol. Surv. India — Pal. Indica — i. Cret. Cepb. of Southern India, 
1861, p. 38, pi. xxiv. ff. 3, 3 « ; pi. xxv. ff. 1, 1 a, 2 (not ff. 3, 3 a). 
^ Ibid. pi. xxv. f. 2. 
