35 
NAUTILUS Sowerbyi. 
TAB. DCXXVIL— fig. 1,2 & 3. 
Spec. Chau. Lenticular, with a rounded edge, 
umbilicated ; septa very convex, their ends 
much recurved and obliquely truncated ; si- 
phuncle very near the inner edge of the sep- 
tum ; aperture triangular, longer than wide ; 
lines of growth suddenly bent very far back- 
wards. 
Syn. Nautilus Sowerbyi, fVelherell in Phil. Mag. 
and Journ. v. ix. 466. Morris, Cat. 183. 
One of the discoveries made by Mr. Wetherell in the 
cutting at Chalk Farm for the Birmingham railroad, in the 
middle part of the London Clay. It also occurs at Bognor, 
as I learn from Mr. Dixon of Worthing, and I have seen 
it from Sheppy. It is a well-marked species, which grows 
to nine inches in diameter. 
Figs. 4, 5 and 6 are added to this plate to show the po- 
sition of the siphuncle and form of the septum in each of 
three other species of Nautilus. Fig. 4 is N. imperialis 
(tab. 1), which has a somewhat triangular septum, wider 
than long, with broad obliquely truncated sides which 
are suddenly reflected, and a siphuncle that recedes from 
the inner margin as the shell increases in size. Fig. 5* 
N. regalis (t. 355) : the septum rather square, no part 
of it reflected, and the siphuncle nearly central. Fig. 6,* 
* 
In some copies these numbers are accidentally reversed. 
