36 
N. centralis (tab. 1), with a semicircular septum, much 
wider than long, regularly convex, without any second 
curvature, and a nearly central siphuncle. These charac- 
ters will be found of importance when imperfect specimens 
are to be examined, as some one or other of them is gene- 
rally to be ascertained. 
NAUTILUS urbanus. 
TAB. DCXXY1II. 
Spec. Char. Discoid, thick, convex, with a round- 
ed margin, umbilicated ; sides undulated when 
old; septum oblong, regularly convex, anteriorly 
narrowed, posteriorly (interiorly) truncated, 
not recurved; siphuncle nearest the inner 
edge; lines of growth not remarkably recurved. 
Syn. N. urbanus, Sow. Morris, Cat. 183. 
A flatter shell than any other tertiary species of Nauti- 
lus except N. ziczac. In common with N. centralis and 
N. regalis , its surface is in the young state concentrically 
striated and the lines of growth beautifully decussated. I 
have long had this in my possession ; it was found in dig- 
ging for the St. Katharine’s Docks near the Tower of 
London. The smaller individual is from Sheppy, and is 
in Mr. Bowerbank’s collection ; it has also been found at 
Highgate. 
