596 



MEGUMI YERI AND TOKIO KABURAKI : 



family : viz., Meixtieria BOCK, Cryptophalus BOCK, Parastylochus 

 BOCK, Stylochus Ehrbg.. Idioplana WOODWORTH, Woodworthia Laid- 

 LA\v and SJulfordia Stummer-Traunfels. The present genus oc- 

 cupies, we think, a position intermediate between Stylochus and Idio- 

 plana. Principal differential points of all the Stylochid genera may be 

 gleaned from the following key : 

 I. Without accessory vesicle to vagina. 



A. "With ductus vaginalis Cryptophallus. 



B. Without ductus vaginalis. 



a. Vagina very long Mcixneria. 



b. Vagina short. 



a 1 . Genital aperture closely approximated. With 



true (sometimes trilobed) seminal vesicle. .. Stylochus. 

 b 1 . Genital apertures distinctly apart from each 



other. With accessory seminal vesicle. .Parastylochus. 

 II With accessory vesicle to vagina. 



A. Accessory vesicle single. 



a. Tentacles absent. Penis slenderly tubular 



Neostylochus, n. gen. 



b. Tentacles present. Penis conical Idioplana. 



B. Accessory vesicle paired. 



c. Tentacles present. Prostatic gland short. . . . Woodworthia. 



d. Tentacles absent. Prostatic gland exceedingly pro- 

 longed Shelf or dia. 



J?r osthi ostomum trilineattim, n. sp. 



Textfigures 4. and 5. 



This species is based on a single specimen obtained on the coast 

 of Hatakejima in Prov. Kii in the summer of 1918. 



Form and Size. — The body in the living state isnearly similar 



