Mr. J. S. Miller on the Genus Actinocamax. 67 



as the lamellar bone is by the Sepia^ and the chambered shell by the Spirula 

 and Nautilus, The chambered shell of the latter class has a structure not 

 altogether dissimilar to that of the lamellar Sepiaceous bone. 



The observations now given on the Actinocamax appear to extend the ap- 

 plication of these analogies to that genus also. It appears to represent the 

 belemnitic guard destitute of its chambered shell: and if the analogy between 

 this part and the lamellar bone of the Sepia shall appear well founded^ the Ac- 

 tinocamax will furnish a beautiful link connecting the Sepiaceous Cephalopoda 

 with the multilocular (the Sepiaria with the Polythalama) of Lamarck : and we 

 shall have a regular series of these animals^ arranging them according to their 

 concretions or appendages as follows. 



A. Cephalopoda with a horny lamina. Loligo. 



B. Cephalopoda with a concretion composed of many concentric lamellae 



(improperly called bone) adhering to each other by transverse laminae 

 placed at intervals^ the curve of these lamellae forming only a portion 

 of a circle. Sepia. 



C. Cephalopoda with a concretion or appendage consisting of similar 



lamellae enveloping or embracing a complete circle : intervals of 

 the lamellae filled with radiating spar secreted at the same time, 



Actinocamax. 



D. Cephalopoda with a similar appendage and a small multilocular shell. 



Belemnites. 



E. Cephalopoda with a multilocular shell and no lamellar appendage. 



Orthocera, Nautilus, Sgc. 



Upon this view, the Belemnite forms the centre of the series, uniting 

 the lamellar appendage and the multilocular shell ; while the extremes on the 

 one hand present the appendage only, and on the other the multilocular only. 



I conclude, therefore, that the animal of the Actinocamax appears to have 

 belonged to the Cephalopoda sepiacea, and its appendage or concretion to 

 have been inclosed within two muscular parts of the animal which formed 

 the two longitudinal portions, and left on their surface the impressions of the 

 blood-vessels passing through the muscular integuments immediately under 

 the secreting epidermis. 



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