122 ART. 2. — H. MATSUMOTO : 



Arms composed of short and wide joints, uniformly tapered. 

 Dorsal arm plates rhomboidal, with very obtuse outer angle, widei- 

 than long, slightly in contact with each other, with a more or 

 less distinct median keel, so that the dorsal side of the arm is 

 keeled as a whole. Lateral arm plates Avith prominent spine 

 ridges, meeting neither above nor below. First ventral arm plate 

 very small, quadrangular, with concave inner side, longer than 

 wide. Those following are moderately large, pentagonal, witli 

 convex but slightly notched outer side and rounded outer angles, 

 about as wide as long. Six arm spines, long, flattened, more or 

 less curved, truncate, translucent, but not serrate ; the uppermost 

 or the next spine is the longest and is about two and a half 

 times as long as the corresponding arm joint, while the lowest 

 one, the shortest, is slightly longer than the same. Two oval, 

 thin, leaf -like tentacle scales to each pore. 



Colour in alcohol : disk grayish brown ; one specimen with five 

 white patches, which correspond to the radial shields, the other 

 without any ; arms banded with grayish brown and white. Tlie 

 grayish brown parts are dark green and the white parts vivid red 

 in life, according to my own observation on board the " Ikuomara." 



This species more or less resembles 0. bidentata in the 

 disk coverings, though precise comparison may be dispensed with. 

 The presence of two tentacle scales to each pore, together with 

 the very fine granulation, makes the present species very easy to 

 be recognised. 



Ophiacantha rosea Lyman. 



Opldacantha rosea : Lym.\n, Bull. Mus. Comp. Zool., V, 1878, p. 139, 

 PL X, figs. 267 & 268; Lyman, Rep. Challenger, V, 1882, p. 148, PL 

 XXV, figs. 10-12. 



