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Systematic guide to the genera and species of Rhizucephala, with anatomical 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 morphologically anterior 

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



e. the face hidden in the diagram. 



Genus Syloil (Kroyer [3]). 

 (See Plate S figs. 1—1.) 

 Diagnosis. External body of adult yellow. 



Roots yellow, widely distributed, branching, without lagenae. 



Mantle and visceral mass muscular, mantle smooth. 



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



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



long axis of host (Plate 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. 

 Colleteric gland median, unpaired, and highly branched (Plate 8 fig. 3). 

 Testes absent. 

 Nauplius not known. 

 Endoparasitic development unknown. 

 Larval males unknown. 

 Parasitic on Decapoda Macrura. 



8. hippolytes (Kkoyer). 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. 



