REPORT ON TIIE ASTEROIDEA. 65 



intermediate in length and robustness between them and the general echinulation of the 

 area above mentioned. 



The actinal interradial areas are large and well developed, and extend as far as the 

 ninth or tenth adambulacral plate. They comprise numerous intermediate plates arranged 

 in more or less regular series between the adambulacral plates and the marginal plates ; 

 the separate plates are to a certain extent indicated by pseudo-sutures and the arrange- 

 ment of the numerous short, equal, papilliform spinelets which they bear. The form of 

 the groups is often rectangular, the papillae are extremely short, and there is no tendency 

 whatever to simulate paxillse, the papillae appearing to spring from the membrane which 

 uniformly covers the whole area. 



The anal aperture is subcentral and distinct, though there is no modification of the 

 paxillce surrounding it. 



The madreporiform body is compound and of great size. It occupies a circular area 

 13 - 5 mm. in diameter, the outer margin of which is two to three mm. distant from the 

 marginal plates. The area is rather higher than the plane of the abactinal surface, and is 

 rendered conspicuous by the greater size of the paxillae which cover it, the spinelets com- 

 posing them being a little longer and more robust. The striated surface is entirely hidden 

 from superficial view. When the spinelets are removed the furrows are seen to be remark- 

 ably fine and to appear to mount the base or pedicle of the paxilla. 



The ambulacral tube-feet have a small mamelon-like conical termination. 



Colour in alcohol, a greyish or yellowish white, with a slightly brownish or warmer 

 shade on the abactinal paxillar area. 



Locality. — Station 246. In the Mid-North Pacific, between Yeddo and San Francisco, 

 near the meridian of 180°. July 2, 1875. Lat. 36° 10' 0" N., long. 178° 0' 0" E. 

 Depth 2050 fathoms. Globigerina ooze. Bottom temperature 35°'l Fahr. ; surface 

 temperature 73° "0 Fahr. 



Remarks. — This species is at once distinguished from all the others in the genus by its 

 broad and comparatively low rays, with the angularly rounded margin and the strong inward 

 bevel of the whole surface of the supero-marginal plates towards the abactinal surface. It is 

 further most conspicuously marked by the presence of the single long secondary spine on 

 the actinal surface of the adambulacral plates behind the furrow series throughout the ray, 



2. Dytaster exilis, n. sp. (PI. II. figs. 3 and 4 ; PI. IV. figs. 9 and 10 : the var. gracilis). 



Pays five. R = 124 mm. ; r = 19 mm. P > 6*5 r. Breadth of a ray near the base, 

 14 mm. 



Rays elongate, very narrow and attenuate, tapering slowly from the base to the extre- 

 mity. Lateral walls rather high and vertical. Interbrachial arcs wide, open, and well- 

 rounded. Disk small. Abactinal area of the disk more or less inflated, especially at the 



(ZOOL. CHALL. EXP. — PART LI. — 1887.) 9 



