440 PHILOSOPHICAL TRANSACTIONS. [ANNO 1794. 



which however here and there bones are seen sticking. And here ends this con- 

 nected series of most remarkable osteolithical caverns, as far as they have beea 

 hitherto explored; many more may for what we know exist, hidden in the same 

 tract of hills. Mr. Esper has written a history in German of these caves; and 

 given descriptions and plates of a great number of the fossil bones which have 

 been found there. To this work we must refer for a more particular account of 

 them. 



XXIII. Observations on the Fossil Bones presented to the R. S. by his most 



Serene Highness the Margrave of Anspach. &c. By the late John Hunter, 



Esq., F.R.S. p. 407. 



The bones which are the subject of the present paper, are to be considered 

 more in the light of incrustations than extraneous fossils, since their external 

 surface has only acquired a covering of crystallized earth, and little or no change 

 has taken place in their internal structure. Thfe earths with which bones are 

 most commonly incrusted, are the calcareous, argillaceous, and siliceous, but 

 principally the calcareous; and this happens in 2 ways: one, the bones being 

 immersed in water in which this earth is suspended; the other, water passing 

 through masses of this earth, which it dissolves, and afterwards deposits on 

 bones which lie underneath. Bones which are incrusted seem never to undergo 

 this change in the earth, or under the water, where the soft parts were destroyed; 

 while bones that are fossilized become so in the medium in which they were de- 

 posited* at the animal's death. The incrusted bones have been previously ex- 

 posed to the open air; this is evidently the case with the bones at present under 

 consideration, also those of the rock of Gibraltar, and those found in Dalmatia; 

 and from the account given by the Abbe Spallanzani, those of the island of 

 Cerigo are under the same circumstances. They have the characters of exposed 

 bones, and many of them are cracked in a number of places, particularly the 

 cylindrical bones, similar to the effects of long exposure to the sun. This cir- 

 cumstance a[)pears to distinguish them from fossilized bones, and gives us some 

 information respecting their history. 



If their numbers had corresponded with what we meet with of recent bones, 

 we might have been led to some opinion of their mode of accumulation; but the 

 quantity exceeds any thing we can form an idea of. In an inquiry into their his- 

 tory 3 questions naturally arise: did the animals come there and die.'' or were 

 their bodies brought there, and lay exposed? or were the bones collected from 

 different places? The lirst of these conjectures appears the most natural; but 

 yet I am by no means convinced of its being the true one. Bones of this de- 



* Bones that have been buried with the ilesh on, acquire a stain whicli tliey never lose; and those 

 which have been long immersed in water, receive a considerable tinge. — Orig. 



