FOSSIL REMAINS OF MOLLUSCA 



FOUND IN THE CHALK. 



CEPHALOPODA. 



Belemnites, Auctorum. 



Animal unknown, enclosing a straight elongated conical, or fusiform calcareous shell 

 or guard more or less pointed below, and pierced above with a conical cavity or alveolus, 

 in which is lodged the phragmacone, a hollow horny cone divided into chambers by nearly 

 horizontal septa, which are traversed on the anterior or ventral margin by a siphuncle. 

 Wall of the alveolus entire. Exterior of the shell marked, in many species, by a furrow 

 down the front, and one down the middle of each side, but without any branching 

 vascular impressions. 



The above description includes all the parts of the Belemnites which have been found 

 in the Chalk ; but in some of the beds of the Oolitic series more perfect specimens are 

 found, in which the phragmacone is produced far above the walls of the calcareous shell, 

 and is provided with two elongated, slender, testaceous processes, proceeding from the 

 dorso-lateral margins of its upper edge; and the whole body is invested with a thin 

 testaceous or comeo-calcareous integument. For full descriptions of these interesting 

 remains the reader is referred to the Memoirs of Professor Owen in the ' Philosophical 

 Transactions of 1844,' and of Dr. Man tell in the volumes of the same work for 1848 and 

 1850, and to the ' Paleontologie Franfaise, Terrains Jurassiques' of M. D'Orbigny. 



M. D'Orbigny separated from the Belemnites those species which have a fissure down 

 the anterior or ventral side of the alveolar cavity, and which are provided with two longitudinal 

 depressions down the dorso-lateral portions of the shell, from which, in some species, 

 proceed branching vascular impressions ; to these he has given the name of Belemnitella. 



1. Belemnites ultimus, jyOrb. Plate I, fig. 17. 



Belemnites minimus, in part? Lister. Hist. Anim. Anglise, tab. vii, fig. 32? 



— LisTEBi, Phillips. Geology of Yorkshire, vol. i, tab. i, fig. 18? 



— ULTIMUS, D'Orbiyny. Paleont, Fran9. Terr. Cret., Supp., p. 24. 



