76 TRACHELIPODA. 



Genus 33.— BELEMNITES — Lamarck. 



Generic Character. — Shell straight, conical, elongated, 

 capable of being separated into two parts, the outer one a 

 solid sheath, produced above and excavated with a conical 

 cell beneath ; the inner nucleus conical, and divided by 

 numerous transverse septa, perforated by a central tube, 



Belemnites subconicus — The Sdbconic Belemnites. 

 Plate X. fig. 29. Lower part semi-cylindrical ; upper part 

 conical and attenuated. Fossil, found in Britain in chalk- 

 marl. 



OEDEE IIL-TRACHELIPOBA. 



Posterior part of the body spirally convolute, separated 

 from the foot, and constantly enveloped in a shell; foot free, 

 depressed, attached to the lower base of the neck, on the 

 anterior part of the body, and forming an organ of locomo- 

 tion ; shell spiral, and enveloping. 



Section I Zoophagous Trachelipoda, 



The animals are entirely marine, having a protruding 

 siphon, and respiring water only, which reaches the branchiae 

 by this siphon; they are devoid of maxillae; provided with 

 a retractile proboscis ; and feed on other animals. 



FAMILY I. INVOLUTA, 



Shell destitute of a canal, but having its aperture notched 

 or effuse at the base, and its volutions compressed, and 

 convoluted so as that the external one nearly envelopes the 



