I 
XAUTILTDja. 
209 
curve backwards on approaching the periphery, where they form a 
shallow sinus. In a young shell (4| inches in diameter, see fig. 40) 
the longitudinal ornaments cover the whole surface of the test, and 
Fig. 40. 
Navfilus ornatus. — a, lateral view of a young shell, showing the open umbilieus 
and the ornamentation of the te.st ; h, front view, showing the position of 
the siphuucle. Drawn from a specimen in the British Museum (No. 51952). 
About half natural size. 
they are in the form of delicate irregularly-spaced ridges, with very 
fine lines occupying the interspaces. The ridges are more numerous 
on the periphery than on the sides of the shell. 
Remarhs. “ The adult characters of the ornamentation of this 
species have been drawn up from a gigantic specimen, 2 feet in 
diameter, which was found at Sherborne, Dorsetshire. This is pro- 
bably one of the largest examples of Nautilus known ; at least the 
writers have never seen any account of a specimen approaching it 
in size. A smaller one from the same locality (Sherborne) measures 
11 inches in its greatest diameter; it is a cast of the septate part 
of the shell, together with a portion of the body-chamber. Frag- 
ments of the test with its characteristic ornaments adhere to the 
cast in one or two places. 
“ This species, in respect to its ornamentation, bears some resem- 
blance to N. Jourdani of the Upper Lias, but can be at once distin- 
guished by its less angular whorls and the rounded margin- of the 
umbilicus. The latter character also distinguishes it from N. tere- 
hratus from the same beds, whose ornaments, like those of the adult 
shell of N. ornatus^ nre almost entirely confined to the peripheral 
PART II. p 
