Systematic guide to the genera and species of Ehizocephala, with anatomical diagnoses. 



Ill 



Mesentery very thin, running in a curve on the right side of the parasite relatively to 



the host, horizontally to long axis of host. 

 Body much compressed laterally. 



Ring of attachment situated at posterior end of mesentery. 

 Colleteric glands paired, highly branched. 



Egg tubes attached to mantle by retinacula (see Note on p. 113 . 

 Testes paired, showing degenerative signs. 

 Nauplius with somewhat elongated frontal horns. 

 Endoparasitic development with active migration of central tumour and with formation 



of perisomatic space. 

 Larval males of common occurrence, not developing beyond Cypris stage. 

 Parasitic on Decapoda Brachyura. 



S. carcini (Thompson [1]). Host of type specimens Carcinus moenas, from North Sea, 

 St. George's Channel, Plymouth, Roscoff, Danish and Norwegian waters. 

 Characters of species those of genus. 



Remarks. I append a list of all the hosts of £. carcini known to me, and the names 

 given to the parasites, arranged according to geographical distribution. 



North Sea, Channel and Bay of Biscay. 



