Gigantostraca. 



83 



Order 2. —Gigantostraca (Eurypterines). 



In the Gigantostraca the sixth (or tifth and sixth) pairs of the J^_ ^^^^^^ 

 appendages of the prosoma are modified to act as paddles. There 

 are twelve distinct somites in the hinder region of the liody 

 (mesosoma and metasoma). 



VI 



^'^ \ 



Fig. 55. 



Restoration of Eurypteriis fischcri (after Holm). a — Appen- 

 dages of prosoma. b — Sternal plate of prosoma. c — Appendage 

 believed to distinguish the female sex, perhaps an ovipositor. 

 D. — Plate-like appendages of mesosoma. The first plate (which 

 corresponds to two somites of the body) is the genital oper- 

 culum. E — Sternal plates of metasoma. 



G 2 



