ASTEROIDEA OF NOBTH PACIFIC AND ADJACENT WATERS — FISHER. 165 



grooves. In NympJiaster these plates have no abrupt furrow, at least in the dorsal 

 series, being like Mediaster. The adnnibulacral armature difTers from that of 

 Nymphaster in having on the surface of the plate spaced from furrow series a row of 

 two or tlirce stouter and longer tapering spines, one of whidi is larger than the other 

 two. The furrow spinelets are long, slender, compressed, and four or five in number. 

 The general facies of this species, as well as the character of the pedicellariae, ally it 

 to Mcdiaster rather than P sen dar chaster. 



Plinthaster Verrill and Pyrenaster Verrill. — The type of Pyrenaster Verrill 

 (1899, p. 166) is Pentagonaster dentatxLs Perricr (1884, p. 242). According to Verrill 

 Pyrenaster "is distinguished from Tosia and Pentagonaster especially by the exis- 

 tence of smaller secondary rounded plates between the primary abactinal i)lates, 

 and also by the greater .specialization of the furrow series of adambulacral spines, 

 for these do not grade into the actinal granulation, as they do in the genera referred 

 to. In this respect the genus is more nearly like Mediasier, etc." I have examined 

 the type, P. dentatus (No. 408, Coll. Mus. Comp. Zool). The onlj^ secondary 

 abactinal intermediate plates, on the radial areas, are one or two proximally. 

 There are a few small plates here and there on the center of disk. But Pentagonas- 

 ter perrieri (No. 418, Coll. Mus. Comp. Zool.) the type of Verrill's Plinthaster (which 

 I consider of generic rank) has secondary plates proximally on the radial areas and 

 also a few on interradial areas. There are more secondary plates than in the tj'pe of 

 dentatus. The adambulacral armature is of the same character in both species. A 

 difference between the two species (but hardl}- of generic importance) is to be found 

 in the shape of the pedicellarise. In dentatus the pedicellarife are few, small, forami- 

 nate, with narrow spatulate slightly tapering chisel-like jaws, while in perrieri they 

 are much larger with broad jaws (nearly as wide as high) which on the actinal sur- 

 face fit into slight depressions of the plate. The abactinal pedicellariffi are of the 

 same form (similar to those of Tosia tuhercuhta Gray) but smaller. In both species 

 a few distal superomarginals are in contact, but this is subject to individual variation. 



I think tiiere is not sufficient difference to make two genera. The general 

 appearance of the two groups is strikingly similar, and added to this the abactinal, 

 actinal, and adambulacral plates are the same. Plinthaster has page priority and 

 should be adopted as the name for tlie enlarged genus. The following arc the 

 species : 



Plinthaster perrieri (Sladen). Plinthaster nitidus (Verrill). 



Plinthaster comptus (Verrill). Plinthaster ceramoideus (Fisher). 



Plinthaster dentatus (Perrier). 



Verrill refers Pentagonaster affinis Perrier to Pyrenaster, but as he did not see 

 the type, his specimens were not correctly identified. I have examined Perrier's 

 type (No. 403, Mus. Comp. Zool.) and it is not a Pyrenaster or a Plinthaster. The 

 abactinal plates are wholly granulated and the radial ones are subtabulate. Second- 

 ary abactinal plates are evident in a .small example about one inch in diameter, but 

 in the type they are not markedly diflcrent in size from the primar}' plates. The 

 species may be referable to Cernrnastcr, although it is by no means typical. 



LiTONOTASTER Verrill, 1899, p. 171; type, Pentagonaster interinedius Perrier, 

 1884, p. 24.3, pi. 5, figs. 5 and 6. — I have seen specimens of the type-species. The 



