JAPANESE NUDIBRANCHS. 47 



denticles are to be seen. I think that this form is probably a 

 new species distinguished by the following characters : 



(1) Colour. In all the specimens the rhinophores and the 

 tip of the tail are conspicuously black or very dark brown. 

 Otherwise the colour is uniform and in the best preserved speci- 

 mens is yellowish brown. The wings have no coloured borders 

 and the head and pericardium are of the same colour as the 

 dorsal surface. 



(2) The arrangement of the dorsal surface. This is similar 

 in all the specimens and I have not seen it in any other species. 

 The pericardium is not ovate but is constricted in the middle. Its 

 length is greater than its breadth but it is short in comparison 

 with the length of the whole animal. The dorsal ridges which 

 run into it are very distinct and the two hindmost, which run 

 backwards towards the tail, are parallel to one another and en- 

 close an area which is differentiated from the back and forms a 

 smooth trench. 



Publ. July 18th, 1913. 



