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



The genital openings of each side are distributed asymmetrically about the anterior free edge 

 of the mesentery, those on the left side (vd.l and ovd.l) being on the rnorphologically anterior 

 face of the visceral mass, those of the right side (vd.r and ovd.r) being on the posterior face, 

 i. e. the face hidden in the diagram. 



Genus Sylon (Kroyer [3]). 

 (See Piate 8 figs. 1 — 4.) 

 Diagnosis. External body of adult yellow. 



Koots yellow, widely distribnted, branching, without lagenae. 



Mantle and visceral mass muscular, mantle smooth. 



Mantle opening paired, situated anteriorly relatively to host (Piate 8 fig. 2). 



Mesentery rather narrow, and very short, running mesially and in the sanie axis as 



long axis of host (Piate 8 fig. 2). 

 Body egg-shaped, dorsal surface greatly shortened and ventral surface enlarged with 



highly marked ventral curvature. 

 Ring of attachment situated at posterior end of mesentery. 

 Colle teric gland median, unpaired, and highly branched (Piate 8 fig. 3). 

 Testes absent. 

 Nauplius not known. 

 Endoparasitic development unknown. 

 Larvai males unknown. 

 Parasitic on Decapoda Macrura. 



S. Mppolytes (Kroyer). Characters of species those of genus. I append a list of 

 hosts, names given to the parasites, and the names of the observers, believing, however, 

 that no anatomical distinctions exist to justify the creation of more than one species. 



Host 



Name of Parasite 



Observer 



Hippolyte pusiola 



$. hippolytis (Kroyer) = 



Schneider, Weber, Hoek 





S. Sehneideri (Hoek [21]) NoTway 



Smith 



Pandalus brevirostris 



S. pandali (Kroyer) Norway 



M. Sars 



Hippolyte incerta 



Norway 



Hoek 



H. polaris 



S. danielsseni (Giard [22]) Norway 



Sabine 



H. securifrons 



S. sarsi (Giard [22]) Norway and 

 Greenland 



M. Sars 



H spinus 



S. Challenger i (Hoek [21]) Nova 

 Scotia and Greenland 



Hoek and Smith 



Hymenodora glacialis 



S. hymenodorae (Sars [18]) 



G. Sars 



Hippolyte fabricii 



Frederikshav 



Smith 



Hippolyte brevirostris 



| 





Pandalus Danae 



. Puget Sound 



Calman (25) 



Sclerocrangon munitus 







