306 



s. GOTO : 



Liiidia yesoensis, n. sp. 



(PI. V, figs. 89-90 ; PI. YI, figs. 91-94.) 



This species is nearly allied to Luidia quinaria, but dis- 

 tinguished from it by the general facies, shorter arms and the 

 greater distinctness of the lateral faces of the arms. Whereas 

 in L. quinaria the abactinal and lateral surfaces of the arms pass 

 into each other without any sharp line of demarcation, they pre- 

 sent in this species two distinct faces separated by a rounded 

 angle. In all the specimens in my hands the abactinal side is 

 uniformly dark grey or black, with only the marginal and most 

 distal parts of the arms of a lighter colour. The dark radiating 

 bands present in L. quinaria are absent in this species. 



The radial ratio may be seen from the following : 



Infer omarginals. — The inferomarginals are broad and short, 

 and coincident with the adambulacrals. At the lateral margin of 

 the plate there is a single, somewhat large, squamiform spine, 

 usually with some irregular fine longitudinal furrows on the 

 actinal surface (PI. VI, fig. 92). On the surface of the plate there 

 can usually be made out one or two rows of squamiform spines, 

 which are relatively broader near the lateral margin and become 

 relatively larger towards the inner side. In many cases only one 



