THE EVIDENCE OF THE CENTRAL NERVOUS SYSTEM 27 



form is Limulus. Crustaceans such as crabs and lobsters are of 

 much later origin, and do not occur in any quantity until the late 



Fig. 8. — A, Pterygotus Osiliensis (from Schmidt). B, Stylonurus Logani (from 

 Woodward). C, Slimonia acuminata (from Woodward). 



Mesozoic period. The earliest found, a kind of prawn, occurs in the 

 Carboniferous age. 



Korschelt and Heider have accordingly suggested the name 

 Palceostraca for this whole group, and Protostraca for the still earlier 



