210 A. E. Verrill — Revision Genera and Species of Starfishes. 



The adambulacral plates are rather narrower than the adjacent 

 actinals. Each bears four or live slender spinules in the furrow- 

 series ; these are terete and rather larger than the actinal spinules; 

 on the actinal side there is a grouj) of 12 to 16 slender spinules, those 

 next the furrow series about the same as the latter in size and form; 

 the outer ones are rather smaller. 



The dentary plates are separated by wide open sutures ; their mar- 

 ginal and surface spinules are like those of the actinal plates. 



The recurved spines are conspicuous and not much compressed, 

 with regularly tapered, very acute, hyaline tips. 



The type specimen has the greater radii 33 to 35™'"; lesser, about 

 20™™. 



The type (No. 9758) was taken in 1881, by the Albatross, oflf 

 Martha's Vineyard, at station 994, in 368 fathoms, mud. A smaller 

 specimen (No. 18423) was taken in 1885, at station 2586, in 328 

 fathoms, in the same region. 



This species is easily distinguished from the two preceding by the 

 thicker margin and disk, shorter rays, larger and fewer marginal 

 plates, more numerous adambulacral spinules, etc. 



Family PLUTONASTERID^. 



Phitonasterince (sub-family) Sladen, op. cit., pp. 2, 60, 1889. Perrier, Exp. 

 Trav. et Talism., p. 251, 1894. 



This group appears to be sufficiently distinct to be regarded as a 

 family. The great group called the family Archasteridce by Sladen 

 and by Perrier is so heterogeneous that it cannot be definitely de- 

 fined, as already explained by me. (See p. 199.) 



In the present group the form i§ stellate, the rays often long and 

 tapered. The abactinal plates are usually very numerous, in the 

 form of columnar j^arapaxillae or protopaxillse, covered with small 

 divergent spinules. They generally have no very definite arrange- 

 ment and the median radial series is often not distinguishable. 



The marginal plates are generally well developed and paired, but 

 are sometimes small. They often bear one or more acute spines. 



The actinal plates are imbricated and generally form rows run- 

 ning from the ambulacral to the marginal plates. 



The pedicellariaj, when present, are usually of simple structure, 

 with two to four papilliform blades. See pi. xxvii, fig. 6. They seem 

 to be lacking in many species. Supra-ambulacral plates are present. 



Nearly all the species of this group are from the deep sea. None 

 are littoral. For the subdivisions see p. 200. 



