280 AET, 2. — H. MATSÜMOTO : 



inner and very convex outer sides ; inner lateral and lateral sides 

 concave, the former being in contact with the lateral arm plates 

 and the latter with the tentacle pores ; longer than wide, wider 

 without than within, in contact with the first plate. The third 

 plate is pentagonal, with concave inner and lateral sides and strong- 

 ly convex outer side, about as wide as long. Those beyond are 

 triangular, with wide inner angle and very convex outer side, 

 wider than long ; separated from one another and constantly 

 diminishing in size outwards. Three arm spines, conical, acute, 

 the uppermost is longer and stouter than the others, and are two- 

 thirds as long as the corresponding arm joints ; in the free basal 

 joints the lowermost two are half as long as the corresponding 

 joints. The second oral tentacle pore opens hardly within the 

 oral slit, with four or five scales on both the abradial and adradial 

 borders. The first four or five tentacle pores have each two 

 scales on the adorai border, but the rest have only one. Besides, 

 the first and second pores have two very small scales on the 

 aboral border, which are almost covered over by the adorai 

 scales. 



Colour in alcohol : disk very light brown, arms white. 



The present species differs from 0. irrorata (Lyman) in the 

 shape of the oral shields, in the longer arm spines, and in the 

 fewer tentacle scales ; from 0. plana (Lütken & Moetensen) in 

 the shape of the radial and oral shields, in the coarser scales of 

 the interbrachial ventral surfaces, and in the fewer tentacle 

 scales ; and from 0. m'lndata in the shape of the radial and oral 

 shields, in the longer arm spines, and in the fewer tentacle 

 scales. 



