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



interior ones^ so as to inclose a conical cavity for the reception of the cham- 

 bered shell; butj following' an inverted arrangement^ permit the interior laminas 

 to rise in succession above them ; so that the centre^ instead of presenting a 

 deep conic cavity^ becomes convex, forming a protruding cone of which the 

 vertical angle is about 45. This is an excellent proof of the non-existence at 

 anytime of a chambered cone in this place; since the structure described, not 

 only affords no traces of a cavity fitted for its reception, but is altogether of 

 an opposite character. From the centre elevation of the base to the circum- 

 ference, radiating ridges extend, widening as they reach it, forming by inter- 

 secting the edges of the enveloping laminae a subtubercular surface, well 

 adapted for adhesion to an animal substance. 



Along each of the two flattened sides is a groove, branching as it approaches 

 the apex, — the evident impression of blood-vessels : in all other parts the sur- 

 face is smooth, and not striated as in the Echinital spines, or provided with a 

 ring near the base, which would essentially serve for the adhesion of a radi- 

 ating muscle, and must therefore have been possessed by it had it been an 

 Echinital spine. 



The above observations demonstrate, that the resemblances between the Ac- 

 tinocamax and the belemnitic guard are not merely general and external, but 

 extend to the minutest points of internal structure; and that both, particularly 

 in regard to Belemnites electricus, present the very essential and remarkable 

 fact, that similar impressions of ramifying vessels may be traced on their outer 

 surface. 



These analogies seem too many and too great to admit any other explana- 

 tion, than that both substances have once formed the analogous parts of ani- 

 mals belonging to the same great natural order; while the important difference, 

 — that one of these bodies has been provided with an internal chambered shell, 

 and the other cannot be supposed ever to have possessed a similar appendage, 

 equally proves them to have appertained to different genera, or perhaps 

 even to different families of that order. 



What that order was, is a question in which we have analogy only to guide 

 us, the whole families of Belemnite and Actinocamax having long vanished 

 from the actual Systema Naturae, or at least having hitherto escaped our re- 

 searches, and being known only from the preservation of their more solid 

 parts in the strata of the earth. 



These analogies, however, are such as to afford probable evidence of a very 

 high degree; and the tendency of that evidence is, as we have before seen, and 

 as is now universally admitted with regard to the Belemnite, to rank it as the 

 appendage of a family of Cephalopodous Mollusca, enveloped by the animal 



