46 Art. 9.— M. Yeri and T. Kaburaki 



Key lo Species of the Polyclads treated of in this paper. 



i. Without ventral sucker Suborder Acotylea. 



a. 1 Marginal eyes present Section Craspedommata. 



a? Without nuchal tentacles. 



0. 8 With a single genital aperture. 



Penis large. Numerous prostates open on walls of penis and antrum. 



Accessory vesicle of vagina horseshoe-shaped Genus Discocelis. 



Body broadly oval, light vinaceous cinnamon, darker in the central parts, 

 with small darkish brown blotches uniformly distributed all over. Tentacular 

 eye-spots in two round, crowded clusters. Cerebral eye-spots in somewhat 

 linear clusters; each cluster divided by brain into an anterior and a posterior 



group 1. D.jajjonica. p. 3, 



i. 8 With 3 genital apertures. 



Witbout true seminal vesicle. Prostate opening into ejaculatory duct 

 by a distinct duct. Penis unarmed. There occurs a duplicate penial system 

 either in front of or behind the functional. A part of vagina forming a 

 prominent compact spiral coil. Vagina and vaginal duct running nearly in 

 a circle and both opening into antrum femininum just within the external 



female aperture Genus Bergendalia. 



Body elongate-slender, of a grayish buff-pinkish colour, with a reddish 

 median streak. Marginal eye-spots in a row or rows around body ; besides, 



numerous eye-spots densely distributed all over the head end 



2. B. diversa. p. 8. 



b. 2 With nuchal tentacles. 



With true seminal vesicle. Prostate separated from ejaculatory duct. 



Penis unarmed. Without accessory vesicle to vagina . . Genus Stylochus. 



c. 8 Body elliptical, of a reddish orange or a brick colour, dotted more or less 



uniformly with minute reddish spots. Tentacular eye-spots confined to basal 



parts of each tentacle ; cerebral eye-spots scattered close together over brain 



region 3. St. rutilas, p. 5. 



d} BoJy broadly elliptical, deep-buffy in colour, dotted more or less uniformly 

 with minute purplish gray pigment spots. Tentacular eye-spots arranged 

 close together on tentacles ; cerebral eye-spots in two bands which diverge 



anteriorly 4. St. ijimai. p. 0. 



b. 1 Marginal eyes absent Section Schematommata. 



c. 2 Prostate along the course of ejaculatory duct. 



e. z With true seminal vesicle and accessory vesicle to vagina. 



With or without tentacles and penial stylet Genus Notoplana. 



a. 4 Nuchal tentacles small, bluntly pointed. Without penial stylet. 



