INTRODUCTION. 



61 



tliere is no imbrication at all, and the edges meet 

 like plates or the flags of a pavement. But one 

 of the more remarkable contrivances for hold- 

 ing them in connection, is seen in some fossil 

 species, where the incumbent scale is furnished 

 with a hook, or tooth, which fits into a corres- 

 ponding hollow in the lower edge of the upper 

 scale, better understood by inspecting the accom- 

 panying cuts of those of (1) Paleoniscus* Freies- 

 kbeni, and (2) Pholidophorus^ macrocejphalus^ 

 Agass. 



The skm is immediately attached to the muscles, 

 the outer lateral layer of which will be seen in 

 the accompanying plate, (PI. XXXI.) One 

 great muscle {a) occupies nearly the whole side, 

 and is almost the only one which is externally 



* •za.Xuioi, ancient ; onvKest oniscus. 



t ^iXihap^os, scale-bearlng, like a snake. 



