Japanese Tricladida Maricola. q 



•of lateral branches, while the posterior trunks are provided with 

 14-18 outwardly directed branches. 



Genital Organs.— The genital aperture is placed at a distance 

 behind the mouth equal to about one-fifth that between the latter 

 and the posterior body-end. The genital atrium is divided into 

 the penis-sheath and the vestibulum by a constriction. Numer- 

 ous testes, of a spherical shape, are dorsally situated in two lateral 

 zones, beginning from the ovarian region and extending behind 

 nearly to the end of the body. The vasa deferentia are united 

 into a slender ejaculatory duct in the bulbous part of penis with- 

 out showing any sign of vesicuhi seminaHs. The penis is of a 

 small conical shape, being vertically disposed in its sheath. The 

 paired ovary is situated ventrally between the first and second 

 pairs of tlie lateral branches of the anterioi- gut trunk. The 

 oviducts open directly into a small outbulging of vagina at tlie 

 postero-inferior aspect. The receptaculum seminis is a large spher- 

 ical body, lying behind the penis. The vagina runs anteriorly 

 and obhquely downwards to join the vestibulum from behind. 



Remark.~Thm species seems to be nearly aUied to Fr. ulvae 

 and Pr. lohata, but may be readily distinguished from the former 

 by the entire absence of pigments and the feature of the oviducts 

 opening directly into tlie vaginal outbulging without uniting into 

 an unpaired terminal duct, and from the latter by the different 

 shape of tlie head and the absence of the seminal vesicle within 

 the penis. 



Stununeria trigonocephala (Ij. et Kab.) 

 (PI. I., figs. 2, 4, 5.— Text figs. 2, 5.) 



A single specimen of this species previously referred to the 

 genus Frocerodes was first collected by the late Professor Ijima in 

 1887 from the coast of Oginohama, Prov. Rikuzen. Later, num- 

 erous specimens were obtained by myself in the estuary of rivulets 

 in the same locality (1915), and in Itsukushima, Prov. Aki 

 (1916). 



Form. — The head pi-esents a nearly triangular sliape and 



