LAMARCK. 537 



b. Shell with a more or less elongated canal at the base of 

 the aperture, the form of the right lip altered at 

 maturity, and with a sinus on the lower part. 



Les Ailees. 



c. Shell with a short canal ascending posteriorly, or with 

 an oblique emargination, semi-canaliculate at the base 

 of the aperture, the semi-canal being directed towards 

 the beak. 



Les Purpuriferes. 



d. No canal at the base of the aperture but a subdorsal 

 sinus, and folds on the columella. 



Les Columellaires. 



e. Shell without a canal, but the base of the aperture 

 emarginate or effuse ; and the volutions of the spire 

 large, compressed, and so convolved that the last covers 

 up almost entirely the others. 



Les Enroulees. 



Order IV. CEPHALOPODES. (August, 1822.) 



I. SECTION. C. POLYTHALAMES. Shell multilocular, com- 

 pletely or partially enveloped, and enchased in the posterior 

 part of the body of the animal, often with organic adhesion. 

 * Shell multilocular with even septa. (The margins of the 

 septa are simple, and do not imprint sinuous and jagged 

 sutures on the internal wall of the shell.) 

 (1). Shell straight or nearly so : not spiral. 



Les Orthocerees. 



(2). Shell partially spiral, the last whorl continued in 

 a straight line. 



Les Lituolees. 

 (3). Shell semi-discoid, the spire eccentric. 



Les Cristacees. 



(4). Shell globular, spheroidal or oval, with the 

 whorls of the spire enveloping or with cells united 

 together in the mantle. 



Les Spherulees. 



(5). Shell discoid with a central spire and cells radiating 

 from the centre to the circumference. 



Les Radiolees. 



(6). Shell discoid with a central spire and cells which 

 do not radiate from the centre to the circumference. 



Les Nautilacees. 



** Shell multilocular with septa jagged and foliaceous on 

 the margins. 



Les Ammonees. 



