116 
NAUTILOIDEA. 
Coelonautilus paucicarinatus, Foord. 
1825. Nautilus multiearinatus (pars), J. de C. Sowerby, Min. Couch. 
vol. V. p. 129, tab. cccclxxxii. f. 2 (excl. f. 1). 
1878. Nautilus cariniferus^ de Koninck, Faune du Calcaire Carbonifere 
de la Belgique (Annales du Mus. Boy. d’lli.st. Nat. de Belgique, 
tom. ii.), p. 134, pi. xxviii. ff. 1-6. {Not of J. de C. Sowerby.) 
Coelonautilus ’paucicarinatus. — a, lateral view, showing tlie central perforation ; 
b, front view, showing the peripheral keels. Drawn from a specimen in 
the Collection. One half natural size. 
Sp. Char. Shell thick, discoid, composed of three volutions, only 
iust touching each other, aU being exposed to view in a very deep, 
step-like umbilicus, in which there is a small central perforation. 
The periphery is very broad and is bordered on each side in the young 
and adolescent shell by sharp keels, but these become obsolete in 
the adult. There is a also a similar keel at the edge of the 
umbilicus, which shares the fate of the former. The periphery in 
the young shell bears also two, sometimes three, keels on either 
side, leaving a wide and slightly hollow area in the centre. These 
keels are scarcely defined in the adult shell, but their place is taken 
by a ridge, or narrow convexity, which extends quite to the edge of 
the aperture. The latter has a similar form to that of C. cariniferus, 
J. de C. Sow. The body-chamber occupies exactly half of the last 
whorl. The impression of the retractor muscle is seen indistinctly 
upon the cast of the body-chamber of a large specimen (registered 
No. 43862) ; and the marks of the mantle, consisting of a series of 
closely arranged, punctured lines, are visible in the same example. 
The septa are approximate, gradually increasing in their distance 
