﻿BRITISH FOSSIL CEPHALOPODA. 



PART I. 



INTRODUCTION. 



General Position of the Cephalopoda in the Animal Kingdom. 



The fossil shells which form the subject of this monograph, and to which the names 

 of Orthoceras, Goniatites, Ammonites, Belemnites, &c, have been applied, so closely 

 resemble those produced by the recent Nautilus, Spirula, and Sepia, that we are com- 

 pletely justified in assuming that the corresponding animals presented a structure 

 similar to the living forms — an assumption which, in some instances, has been verified 

 by the discovery of parts of the body preserved in a fossil state. To the assemblage 

 of these animals, including those naked or soft-bodied ones, which we know as 

 Octopods or Polypes, Aristotle gave the name Malahia, and separated them from the 

 ordinary shell-bearers, which he called Testacea. Cuvier, however, demonstrated a 

 general uniformity of internal organisation throughout the several classes of the 

 Mollusca, in which he included both of Aristotle's subdivisions, and, separating 

 the several classes by means of their real or supposed organs of locomotion, named 

 the objects of our present study the Cephalopoda. 



The Mollusca may be very shortly defined as animals which show in the 

 anterior or oral end of their body a bilateral symmetry, but are never divisible into 

 segments, which are provided with a tubular alimentary canal, and whose nervous 

 system consists of three principal pair of ganglia — the alimentary canal passing 

 between the commissures of the first and second pair. The tegument is usually 

 formed into a free fold called the mantle, from which may be developed branchiee 

 on one side and a shell on the other. In the possession of a distinct head, and of 

 that remarkable organ in the floor of the mouth, known as the tongue, or odonto- 

 phore, the Cephalopoda belong to that division of the Mollusca which was first called 

 Glossophora by Loven in 1847, 1 and at a later period Odontophora by Huxley ; and 

 it is with the higher classes of that division, the Gastropoda and Pteropoda, that 



1 Kongl. Vetenskaps Akad. Handlingar for ar 1847. 



