DEVONIAN ERA. 



95 



occurrence of reptiles the earliest of their class positively 

 known to geology, if British observers be not mistaken 

 as to the relations of the strata in which their remains 

 have been detected. Of these crustaceans, found chiefly as 

 yet in Forfarshire and Hereford, we know too little to 

 assign to them their exact place in existing classification ; 

 but if concentration and specialisation of organs are to be 

 tests of higher and lower, then we are compelled to place 

 them rather low in the class to which they belong. Like 

 many extinct forms, the eurypterites partake of the char- 

 acters of several adjacent orders, and thus, like the dis- 



1, Styionurus Powriei; 2, Pterygotus Anglicus (ventral aspect). SVorn the Lower 

 Old Redof Forfajsh:re. 



covered portions of some ancient mosaic work, they fill 

 up the gaps, and bring out more clearly the continuity of 

 the design that runs throughout the whole. King-crab- 

 like in their carapace and organs of mastication, lobster 

 like in their prolonged and segmented bodies, furnished 

 with broad paddle -like swimming limbs, and frequently 



