598 



FISHES OF THE OLD RED SANDSTONE. 



I next obtained from Dr. Mantell a smooth spine of the Spinas acanthias (the common " Bone 

 Dog" of our shores). 



The analysis of these two bodies was most obligingly undertaken by Dr. Bostock, who has arrived 

 at the following conclusions 1 . 



" The larger of the bodies, Trygon, was first examined • the weight of the whole was very nearly 

 60 grains. For the purpose of ascertaining the proportion of the animal matter to the earthy salts, 

 portions of it were respectively exposed to a red heat in a platina crucible for about half an hour, 

 and digested for 24 hours in diluted muriatic acid. By comparing the results of these processes it 

 appeared that the proportion of the animal and earthy ingredients was as 35*1 to 64*9. The muri- 

 atic solution was then examined, and was found to consist of a combination of the phosphate and 

 the carbonate of lime, in the proportion of 49*15 to 15*65, making the composition of the entire sub- 

 stance as follows : 



Animal matter 35*1 



Phosphate of lime 49*15 



Carbonate of lime 15*65 



Loss 0*1 



100*00 



" The structure both of the animal and the earthy matter appeared to be entirely fibrous, without 

 any cellular or laminar arrangement, as is generally the case in bone, at least in the bones of the 

 mammalia. The whole of the body presented an homogeneous appearance, there being no central 

 cavity nor any obvious difference in the structure or consistence of its different parts. 



"The smaller body (Spinax acanthias) differed essentially in its structure from the above; it 

 consisted of an external shell, containing a quantity of loose membranous matter very similar to the 

 root of a quill. The external shell differed obviously from the larger body in not exhibiting any 

 fibrous appearances, so that when it had been either calcined or acted upon by the acid it lost its 

 form, in the first case being reduced to a number of irregular fragments, and in the latter to a mere 

 pulp. The proportion of animal and earthy matter seemed to vary considerably in its different parts, 

 the former predominating in the root and the latter in the tip. This body also differed essentially 

 from the larger in the nature of its earthy salts, which were found to consist almost entirely of the 

 phosphate of lime, the carbonate being in a very small and nearly inappreciable quantity. The total 

 weight of the smaller body was 4*9 grains." 



This analysis of Dr. Bostock has, therefore, effected the desired object. It enables us to infer, 

 that the original views of M. Agassiz concerning the nature of ichthyodorulites are completely borne 

 out ; for the quantity of earthy and bony matter in these dorsal spines of existing cartilaginous 

 fishes is so great, particularly in such fishes as the Trygon, Myliobatus, Cephalopterus, fyc, that 

 we may well conceive how, if imbedded in sand or mud, such bodies might be preserved as per- 

 manent relics, while every trace of the other parts of the soft and easily destructible animals to which 

 they belonged would be entirely obliterated. 



1 Dr. Bostock will, I hope, soon add to his well-earned reputation as a physiologist by completing an ex- 

 tensive analysis (in which he has already made much progress) of fossil organic remains of all ages, indicating 

 the processes by which they have been converted into their present condition. 



