MOLLUSCA FROM THE GREAT OOLITE. 



SUB-KINGDOM-MOLLTTSCA. 



Class — Cephalopoda. Cuvier. 



Cephalopodes, Lamarck; Ferussac. 

 Cephalophores, De Blainville. 



The remains of the Cephalopodous mollusca may generally be considered of extreme 

 rarity in the Great Oolite, in proportion to their abundance in the Inferior Oolite, and Lias 

 below, and the Kelloway rock and Oxford clay above that formation. Limited, however, 

 as the numbers were of the class at this particular period, the two principal orders into 

 which naturalists have divided the Cephalopoda, viz., the Dibranchiata and Tetrabranchiata, 

 were at that time fairly represented in the Nautilus, Ammonite, and Belemnite, the two 

 latter genera being well known as typical and characteristic of the secondary period of 

 geologic history. 



Class. 1 



Cephalopoda. 



Order. 



Group. 



Family. 



Genus. 



Dibranchiata. 



Oigopsidae. 



Belemnitidse. 



Belemnites. 



(Acetabulifera, D'Orb.) 









Tetrabranchiata. 





J Nautilidse. 

 [Ammonitidse. 



Nautilus. 



(Tentaculifera, D'Orb.) 





Ammonites. 



Order - Dibranchiata. Owen. 



Family — BelemnitiDjE. 



Belemnites, Ehrhart, 1727. Lam., Blainv., Voltz, D'Orb., &c. 



Nautilus Belemnita, Gmelin. 



Acamas, Achelois, Callirhoe, Cetocis, Chrysaor, Hibolithes, Paclites, 



Porodragus, Thalamus, Be Montfort, 1808. 

 Notosiphites, Gastrosiphites, Buval. 

 Belemnites, Pseudobelus, Blainville, 1827- 

 Belemnita, Fleming, 1828. 



An elongated, conical, or fusiform body, of a radiated fibrous structure (the osselet, 

 or guard), solid posteriorly, and more or less pointed (the rostrum) ; anteriorly pro- 



1 For a concise and interesting account of the general characters and classification of the Cephalopoda, 

 the reader is referred to a previous Monograph, by Mr. F. Edwards, 'On the Eocene Mollusca,' Part I, 

 Cephalopoda. 



