DENNIS, ON FOSSIL LIAS. 265 



between them, either in size, shape, or number of the canali- 

 culae. Nor do we meet with better success in viewing the 

 plates on saurians : most of them much exceed the fossil in 

 the size of their lacunae, and those that do not, differ in form. 

 We are therefore obliged, so far as Mr. Quekett's book is 

 concerned, to turn to his plates on Mammals, when at once 

 we cannot help noticing a striking similarity, especially when 

 we come to the sloth, and even more so when we reach 

 Plate XL, and find ourselves amongst the cetaceans. The 

 mammalian characters of the lacunae and canaliculi of the 

 fossil in question, are certainly unquestionable ; and besides 

 this, there is a very striking similarity in them to those of the 

 edentata and cetacea. 



I shall now attempt the proof from my own practical observ- 

 ations ; and let me here observe, that if any person wishes to 

 make himself acquainted with the structure of bone, the best 

 way is for him to do as I have done — grind for himself every 

 bone he can lay his hands on. It is a matter more of time 

 than of difficulty, except in the manipulation of fossil bone, 

 which requires all the care imaginable. Above all, let him 

 not put recent bone near Canada balsam, as all the minute 

 structure of bone is destroyed by it, unless polarised ; and 

 even the canaliculi and lacunae are filled with the balsam, 

 and often obliterated. Old or burnt Canada balsam should be 

 used when any is required, as is the case often in fossil bone, 

 when the canaliculi require to be better exhibited ; and 

 as the small passages of fossil bone are generally filled up, 

 the balsam, of course, cannot then enter, while it has the 

 advantage of making other parts of the bone more trans- 

 parent,* 



Some of the fossil fishes with which our bone was a con- 

 temporary were remarkable, some for the massive character of 

 the scales, and others the armature of their jaws. Through 

 the kindness of Mr. Adams,t a gentleman residing at Buriton, 

 Petersfield, and who has in his cabinet some interesting 

 Stonesfield fossils, I have been enabled to examine the struc- 

 ture of the jaws of the Lejndotus and Pycnodus : the structure 

 of the former tubular, something like the fistularia ; the latter 

 I have figured, as its lacunae and canaliculi well illustrate the 

 icthic characters when they are present in fish, which are as 

 follows : — lacunae of irregular shape, often stellate ; canali- 



* I have obtained the best sections by the aid of marine ghie. 



t This gentleman has also enabled me to figure a fossil saurian from 

 Stonesfield, tig. 5 ; it compares almost exactly with the crocodile (vide 

 D and E of Plate), and is well worthy of notice from its showing that 

 nature has not deviated from her primeval plan. 



