REPORT ON THE ASTEROIDEA. 99 



spines. The spines are short, increasing slightly as they approach the mouth, the outer- 

 most heing much smaller than any of the others. They are slightly subclavate and 

 slightly curved, and radiating apart form an elegant armature. The actinal surface of the 

 plate is covered with numerous short, obtuse, papilliform spinelets, which increase in 

 length and robustness as they proceed towards the inner end of the mouth-plates, those 

 next the marginal series being nearly equal to them in length and very much more robust. 



The actinal interradial areas are large and well-developed, and occupied by plates 

 arranged in regular series or columns passing from the adambulacral plates to the marginal 

 plates. Five or six plates may be counted in the series on each side of the median inter- 

 radial line, and each of the plate3 in the column imbricates slightly on the next outward 

 plate. Naturally the number of plates in a column decreases as the columns proceed' 

 along the ray, and no intermediate plates extend beyond the ninth or tenth adambulacral 

 plate. The intermediate plates adjacent to the adambulacral plates are equal in breadth 

 to the length of the adambulacral plates, and the succeeding plates in a column diminish 

 slightly as they proceed outward. The surface of the intermediate plates is covered with 

 short, uniform, papilliform granules, which form regular rectangular groups, each group 

 being marked out by distinct and well-defined suture-lines or channels from those adjacent, 

 the regularity of the arrangement of the plates being very conspicuous. 



The anal aperture is subcentral, but often inconspicuous, as there is nothing in the 

 character of the paxillse in its neighbourhood to indicate its presence. 



The madreporiform body is obscure and hidden by paxillse, a group of two or three in 

 that position being rather larger than any of the others on the abactinal surface. The 

 position is about one-third of the distance from the margin to the centre. 



The ambulacral tube-feet are large and conical, with a small mamelon-like subcorneal 

 termination. 



Colour in alcohol, a greyish white, with a slightly darker or ashy shade over the 

 paxillar area. 



Locality. — Station 73. West of Fay al, Azores. June 30, 1873. Lat. 38° 30' 0"N., 

 long. 31° 14' 0" W. Depth 1000 fathoms. Pteropod ooze. Bottom temperature 39°'4 

 Fahr. ; surface temperature 69°'0 Fahr. 



Remarks. — Plutonaster notatus is most nearly allied to Plutonaster abbreviatus, but 

 is distinguished by the broad disk and very narrow rays. These characters also serve 

 to separate it at a glance from the other species ; and it is further distinguished by the 

 absence of any spines either on the superior or inferior series of marginal plates. In 

 the largest example in the collection, however, minute or rudimentary representatives of 

 infero-marginal spinelets are present on the plates in the interbrachial arc. 



6. Plutonaster abbreviatus, n. sp. 



Rays five. R = 20 mm. ; r= 7'5 mm. R>25r. Breadth of a ray between the third 

 and fourth supero-marginal plates, 5 mm. 



