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



Ili 



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



the host, horizontally to long axis of host. 

 Body much compressed laterally. 



King 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 centrai tumour and with formation 



of perisomatic space. 

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

 Parasitic on Decapoda Brachyura. 



S. cardili (Thompson [1]). Host of type specimens Carcinus maenas, 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 ali the hosts of S. carcini known to me, and the names 

 given to the parasites, arranged according to geographical distribution. 



North Sea, Channel and Bay of Biscay. 



Host 



Name of Parasite 



Locality 



Carcinus maenas 





s. 



carcini (Thomp.) 



Littoral, widely distributed, very 

 common at Roscoff 



Platycarcinus pagurus 





s. 



triangulus (Anderson [7]) 



Firth of Forth, Bretagne 



Portunus holsatus 





s. 



andersoni (Giard [24]) 



Wimereux 



P. pusillità 









Devonshire 



P. marmoreus 





s. 



belli (Giard [24]) 



Wimereux 



Platyonychus latipes 





s. 



betencourti (Giard [24]) 



Wimereux 



Herbstia nodosa 





s. 



herbstiae (Hesse [8]) 



France 



Pisa gibsii 





s. 



gibsii (Hesse [8]) 



France 



Stenorhynchus phalangii 



m 



s. 



fraissei (Giard [19]) 



Concarneau 







s. 



phalangi (Hoek [13]) 



Heligoland 



Hyas coarctatus 









Danish waters, very common, 



10y 2 fthms. 

 Danish waters 



H. aranea 





s. 



infinta (Leuckart [5]) 



Heligoland 



Inachus dorsettensis 









Danish waters, 9Y2 fthms. 



Lispognathus thompsoni 



(Norm.) 







North Sea, Lat. 49° 25 N., 12° 20 W. 

 1180—1275 meters 



