TRACHELIPODA. 65 



Orthocera Raphanus. — The Radish- Root Orthocera. 

 Plate X. fig. 28. Erect, conically elongated, with longitudinal 

 continuous ribs ; white. Inhabits the Mediterranean sea. 



Genus 33.— BELEMNITES— Zanzarc^. 



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 multilocular, divided by numerous 

 transverse septa, perforated by a central tube. 



Belemnites subconicus The Subconic Belemnites. Plate 



X. fig. 29. Lower pare somewhat cylindrical ; the upper part 

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



ORDER III.— TRACHELIPODA. 



Posterior part of the body spirally convolute, separated from 

 the feet, and constantly enveloped in a shell ; foot free, de- 

 pressed, attached to the lower base of the neck, on the anterior 

 part of the body, and forming a member of locomotion ; shell 

 spiral, and enveloping. 



Section I — Zoophagous Trachelipoda. 

 The animals are entirely marine, having a protruding syphon, 

 and respiring water only, which reaches the bronchia by this sy- 

 phon ; they are devoid of inanillae ; provided with a retractile pro- 

 boscis; and feed on other animals. 



FAMILY I. INVOLUTE. 



Shell destitute of a canal, but having its aperture notched 

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

 luted in such a maimer as the external one nearly envelopes the 

 others. 



Genus 1— CONUS.— Zkn««s 



Generic Character. — Shell turbinate, aperture longitudinal, 

 linear, entire, narrow, and effuse at the base ; pillar smooth, 

 destitute of teeth ; shape of a reversed cone. 

 i 3 



