50 Mr. J. S. Miller on Belemnites. 



IV. Particular Remarks on the internal chambered Cone of the Belemnite. 



It appears that the part of the animal's body which was once contained in 

 the outer chamber secreted a thin layer of a spathose fibrous texture, and that 

 a thin coat resembling nacre but not iridescent, covered the fibrous spathose 

 layer externally and internally, and cemented the whole strongly together. 

 It is evident that the external nacreous investment of this first lamina forming: 

 the chambered cone, could not be formed by that portion of the animal which 

 was within the cone, but was secreted by parts encompassing it. The exterior 

 surface of the cone is, however, less smooth than the interior, and offers 

 thereby an admirable contrivance for its adhesion to the sides of the guard ; 

 proving also, clearly, that it does not result from the same portions of the 

 animal which form the guard, and that this was formed subsequently. 



As the portion of the animal within the cone increased in size, so it enlarged 

 its encompassing shell at the upper margin, at the same time forming a trans- 

 verse concave thin lamina at a short distance from the bottom of its shell, and 

 carrying its sides for some height upwards, thereby affixing the lamina and 

 strengthening the sides of the conical shell. Thus an inner chamber was formed, 

 from which the animal was completely excluded, and with which it only com- 

 municated by its siphuncle extending on one side into it. The siphuncle 

 appears to have been encompassed by a spathose lamina connected above and 

 below with the transverse one, and affixing laterally to the conical shell. 



Each transverse septum is composed of three or four spathose laminae, sepa- 

 rated from each other by the investing nacreous layers just described. The 

 sides of the upper laminse are carried up to nearly the same point where those 

 of the first formed laminae terminate : each, however, successively becomes a 

 little shorter, and thereby forms a circular rim on which the transverse lamina 

 forming the next chamber rests. Hence there results a series of concave cups, 

 whose edges take a conical direction and whose sides adhere to a thin encom- 

 passing conical shell, thereby strengthening the latter, and forming an assem- 

 blage of chambers, through the whole of which the siphuncle extends. 



These laminae exhibit throughout a fibrous and spathose structure, the di- 

 rection of the fibres always forming radii to the curvature of the part. They 

 are covered above and below with a nacreous investment, which being opaque 

 or differing in colour, exhibits when the shell is dissolved in diluted acid clear 

 traces of the animal matter forming fine pellicles. The preservation of these 

 pellicles appears to me to afford an argument in confirmation of my views, — 

 that the intermediate layers of fibrous spar belonged to the original texture of 

 the shell, and are not the result of subsequent infiltration; otherwise it appears 



