184 A. M Verrill — Revision Genera and Species of Starfishes. 



Mediaster Patagonicus (Sladen). 



Pentagonaster Patagonicus Sladen, op. cit. , p. 269, pi. xlvi, figs. 1, 2 ; pi. 

 xlix, figs. 3, 4, 1889. 



This species has rather small, sessile, somewhat elevated pedicella- 

 riae, sparingly scattered on the abactinal and superior marginal plates ; 

 their blades are usually chisel-shaped or spatulate, and vai'iable. Simi- 

 lar ones occur sparingly on the adambulacral plates. Larger ones, 

 with broader valves, occur on the actinal plates ; some of them have 

 three or four blades. The dorsal marginal plates and some of the 

 ventral ones have a small central naked area. 



Near Atlantic entrance to Straits of Magellan, 55 fathoms ; off 

 entrance to Smyth Channel, 245 fathoms. 



The Mediaster roseus (Alcock, 1893, p. 98), from India, 740 

 fathoms, is not a true llediaster. It appears to belong to Pseudar- 

 chaster and resembles P. granuliferus V. 



Njnnphaster Sladen. 



Nymjjhaster Sladen, Nan-ative Chall. Exp., i, p. 612, 1885. Voy. Chall., vol. 



XXX, p. 294, 1889. 

 Pentagonaster (pors) Perrier, Etoiles de Mer, p. 233, 1884. 

 Dorigona Perrier, Exp. Trav. et Talisui., p. 365, 1894 (not of Gray, 1866, p. 7, 



nor of Perrier, 1876, p. 44.) 



Plate XXVI. Figure 7. 



This genus is closely allied to 3fediaster. It differs chiefly in hav- 

 ing, in the typical species, the dorsal marginal plates in contact 

 medially for the greater part of the length of the rays. The charac- 

 ter of the pedicellarige, adambulacral plates and spines, jaws, and 

 marginal plates is essentially the same in both, though the pedicel- 

 lariae are usually higher and spatulate in this genus. 



The abactinal radial paxillfe, in the papular areas, differ in struc- 

 ture from those of Jfediaster. In iV. ternalis these plates, when 

 separated, have no basal connecting ossicles, so characteristic of the 

 latter. They are short, thick, columnar, with the basal portion 

 somewhat swollen and slightly six-lobed ; they articulate by means 

 of the lobes, while the papular pores are situated in the spaces 

 corresponding to the emarginations. The lobes are so slight that 

 they can hardly be called stellate. The stellate appearance, as seen 

 from the exterior, is due to the radial connecting bands of soft tissues 

 between the pores. These plates are less stellate at base than those 

 of Pseudar chaster, and rather more so than those of Plutonaster. 



