A. E. Yerrlll — Revision Genera and Sj^ecies of /Starfishes. ISl 



Mediaster Bairdii Venill. 



Archaster Bairdii Verrill, Amer. Journal Sci., vol. xxiii, p. 139, 1882. 



Isaster Bairdii Verrill, Proc. U. S. Nat. Mus., vol. xvii, p. 258, 1894. Amer. 

 Journal Sci., vol. xlix, p. 136, 1895. 



Mediaster stellatus Perrier, Mem. Soc. Zool. de France, iv, p. 268, 1891. Re- 

 sults des Campag. Scient., fas. xi, p. 46, 1896, pi. iv, figs. 1-1''. 



Plate XXIV. Figures 1-9. Plate XXVI. Figures 8, 8a. 



A comparison of this species with the type-species of Stimpson has 

 convinced me that they are very closely allied and should be referred 

 to the same genus, though the Atlantic species is often nearly or 

 quite destitute of pedicellarire. But when pedicellarije do occur 

 they have nearly the same valvular forms seen in those of M. oequaUs, 

 though they are narrower and more elevated. 



Mediaster Agassizii, sp. nov. 



Five-rayed; regularly stellate, with a large disk and rather long 

 tapered rays. Radii nearly as 1 : 3. Interradial angles are broadly 

 curved. 



Marginal plates large, nearly square, slightly convex, but not 

 swollen ; 36 dorsal and 38 ventral ones in the type, on each of the 

 five sides ; the transverse sutures between those of the upper and 

 lower series are narrow and shallow and usually do not coincide. 



The upper plates are sparsely granulated centrally, having only a 

 few rather distant, rounded granules ; their margins are surrounded 

 with a close row of angular granules, but these do not form distinct 

 fascioles. Some of the upper marginal plates have also small valvu- 

 lar pedicellariae. 



The lower marginal plates are coarsely granulated over the whole 

 surface, the granules being larger than those of the upper ones ; 

 most of them also have one to three or more, oblong, valvular pedi- 

 cellariae, larger than those of the upper plates. 



The abactinal plates are regularly arranged in radial series, very 

 unequal in size, mostly roundish in outline, naked in the middle, but 

 with a marginal row of coarse angular granules. 



Many of them have a central, lai'ge, oblong, valv^jilar pedicellaria, 

 sunken in a pit ; on the larger plates the pedicellaria is about one-half 

 the diameter of the plate, but on the smaller plates it often occupies 

 nearly the entire breadth of the top. Some of the plates lack the 

 pedicellaria and have a central granule in its place. The valves of 

 these pedicellaria^ are usually higher than broad, with the blade 

 broadly spatulate distally. 



