ASTEROIDEA OP NORTH PACIFIC AND ADJACENT WATERS — FISHER 79 



are very irregular. There are about three series of dorsolateral skeletal meshes: A 

 series of larger meshes (or alternating larger and smaller) adjacent to the carinals; 

 a similar series adjacent to superomarginals; between these a very irregular series of 

 quite small intervals. 



Papulae numerous abactinally, arranged in transverse rows conforming to the 

 trend of the skeletal intervals; intermarginal papular areas small, about one papula 

 to an area. 



First 10 or 12 adambulacral plates are triplacanthid, the rest diplacanthid, the 

 spines, in close transverse series, being slender, terete, blunt, about 2 mm. long. The 

 outer spine of the diplacanthid plates is commonly a shade longer and stouter than 

 the inner, while that of the triplacanthid plates is slenderer, tapered, and sharp. 

 The spines of the first 10 or 12 plates are a trifle longer and slenderer than the others. 

 Rarely a proximal plate has a small fourth spinelet. 



The mouth plates are rather broad and carry two slender actinostomial spines 

 (the inner the longer and subequal to or a little longer than the median suture), and 

 three longer, slender, suboral spines — two parallel to suture and one near outer fur- 

 row corner. There are sometimes one or two small, toothed, lanceolate or lanceolate- 

 obtuse, narrow-jawed straight pedicellariae on actinostomial margin. The first 

 postoral adambulacral plates are not joined by the interradial ends, but there is a 

 rather conspicuous interval between them. (PI. 30, fig. 4.) 



Crossed pedicellariae numerous, similar to those of T. galapagensis (Ludwig) 

 and much smaller than the pedicellariae of T. cocosanus (Ludwig) ; length about 0.3 

 mm. They are found on all plates except the oral and adambulacral, and tend to 

 form transverse groups abactinally. They are generally absent from the papular 

 areas. Small lanceolate straight pedicellariae (about 0.45 mm. long) occur along 

 the furrow margin. The jaws are narrow and tapering. Larger ones with a few 

 small terminal teeth occur on the oral plates sparingly. (See pi. 30, fig. 2, stoichodes; 

 fig. 3, cocosanus; pi. 31, fig. 1, galapagensis.) 



Madreporic body large (diameter 2.5 mm.) situated on the margin of the small 

 disk. 



Furrow rather narrow (3 mm.); tube-feet quadriserial along the proximal third 

 of furrow, biserial distally. Ambulacral pores in two very zigzag series on proximal 

 fourth of furrow, and, in this area, very narrow and slit-like; on remainder of ray 

 they form two straight series and are more broadly elliptical. 



Type.— Cat. No. E. 1424, U.S.N.M. 



Type-locality— Station 4230, off Indian Point, vicinity Naha Bay, Behm Canal, 

 southeast Alaska; 240 to 108 fathoms, rocky; bottom temperature, 42.4° F. 



Remarks. — T. alaskanus differs from T. galapagensis (Ludwig) in several impor- 

 tant particulars. I have examined the type of galapagensis which is quite small (R 

 23 mm.). It has solitary, tubercular, heavy, abactinal and superomarginal spinelets 

 like those of T. cocosanus (Ludwig), and its major inferomarginal spiuo is flattened 

 and lanceolate, somewhat almond-form. The oral plates have but two spines, while 

 the numerous abactinal and marginal straight pedicellariae are absent in alaskanus. 

 Both species have diplacanthid adambulacral plates. In galapagensis a few of the 

 proximal plates have a third smaller spinelet. 



