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. DCXXVIII. 



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. Montis, Cat. 183. 



A FLATTER shell than any other tertiary species of Nauti- 

 lus except A^. ziczac. In common with N. centralis and 

 N. regaliSi 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. 



