52 



AET. 2. — H. ÄIATSUMOTO 



paj)illa3 appear to have been overlooked by Kœhlek and Dödekleix, 

 but they are present in the form of several flat, smootli, pave- 

 ment-hke grains, which are however not veiy distinct in larger 



specimens, bnt are more 

 prominent and papilliform 

 in smaller ones. Kœhlee, 

 Clakk and Dödeelein er- 

 roneously call the depression 

 just outside the tentacle pore 

 large tentacle pore, but this 

 large depression is distinct 

 from the pore itself. Dödee- 

 lein doubts the taxonomic 

 value of this depression, but 

 it is present in all my speci- 

 mens and in no other species 

 in my knowledge. I have 

 examined pieces of arms of 

 the foregoing and the present species after boiling them in potash. 

 In A. caudatum, the bar-like lateral arm plates are stout, with 

 much widened adradial ends, and the ventral arm plates are 

 divided into right and left halves, so that the spaces for tlie 

 tentacles are very small. In A. japon'icum, the bar-like lateral 

 arm plates are very slender, with feebly widened adradial ends, 

 and the ventral arm plates are very small and granuliform, so 

 that the spaces -for the tentacles are very large. Thus, I have no 

 doubt that, the depression in question of the present species is a 

 specific character. 



I have compared Ophiocreas i^cipillatus Clakk, A. enoshimanum 

 Dödeelein and A. monacanthum Dödeelein with the corresponding 



Picf. 14. AsteroscJienm {Ojjhiocreas) jajjonlmm. xi 

 a. From above, h. From below. 



