NOTES ON TWO NEW SPECIES OF JAPANESE POLYCLADS. 



597 



to that of other species of the genus. The broadly rounded head is 

 without tentacles of any sort, and passes behind into the trunk, from 

 which it is distinctly marked off. When fully extended the trunk is 

 elongate-slender, and is nearly uniformly broad for a great part of its 

 length, but tapers at the posterior end to a point. The dorsal surface 

 is slightly raised in the median parts from behind cerebral eyes. The 

 sucker and the mouth occur as usual in the median line, the former 

 nearly in the centre of the body and the latter close behind the 

 brain. 



In the creeping state the specimen measured about 20 mm. in. 

 length and about 4 mm. in breadth in the anterior parts. 



Fig. 5. 



Fig. 5. Eye-spots, cerebral and marginal, 



of Prost/u trilineatum. 



Colouration. — The dorsal surface is 

 generally of a milky white colour, showing 

 two well-defined, longitudinal, black bands, 

 running along either side of a median yellow 

 stripe, beginning from behind cerebral eyes 

 and extending nearly to the posterior body-end. The head exhibits 

 a black transverse marking of a broadly arc-like shape, of which 

 the convex anterior side is edged with an yellow border of a 

 crescentic shape, while the posterior side is notched in the middle. 



Fig. 4. Prostfiiostomum 

 trilineatum, n. sp. in 

 the living condition. 



