1 68 VERRILL 



Genus Orthasterias Verrill, nov. 



Long-rayed diplacanthid starfishes with a small disk. Dorsal 

 skeleton consists of stout, wide, subimbricated, four or five-lobed 

 plates arranged in three, five, or more definite longitudinal radial 

 rows, and sometimes with extra interpolated flat ossicles, the rows 

 connected by transverse ossicles. The principal plates bear, on a 

 central boss, large, isolated spines, standing in three to five or 

 more longitudinal rows. The transverse ossicles are strong, oblong- 

 elliptical. 



Usually one row of interactinal or peractinal plates, with or with- 

 out spines, closely united to the adambulacrals and inferomarginals ; 

 sometimes they are rudimentary, and without spines; rarely two 

 rows. 



The inferomarginals are strong, four-lobed plates, each bearing 

 usually two large spines. Superomarginals are large, usually 

 monacanthid, four-lobed; the descending lobe is large and usually 

 joined directly to the inferomarginals, by overlapping the upper lobe 

 of the latter. The alternate supermarginal plates are usually with- 

 out a spine in all of our species except O. forreri, O. leptolena, and 

 perhaps O. koehleri. 



Seen from the interior, the dorsal skeleton is largely composed of 

 the stout connective ossicles, mostly in transverse positions, and some- 

 what reticulated. 



This genus is represented on the Atlantic coast of the United 

 States by O. tanneri Ver. and by 0. subangulosa Ver. (=Asterias 

 angulosa Per., name preoccupied) in the West Indies. O. eustyla 

 (Sladen) seems also to belong to the genus. 



The lateral and dorsal major pedicellariae are unusually large, and 

 are usually of two or more forms. The larger are erect, wedge- 

 shaped, stone-hammer-shaped, or ovate, with the tips of the valves 

 wide and usually denticulate. Others are more slender, with the 

 valves spatulate or narrowed in the middle and the tips unguiculate, 

 with interlocking teeth. Others similar, or smaller, with acute tips, 

 often occur on the adambulacral spines and margin. Type, 

 O. columbiana V. 



ORTHASTERIAS COLUMBIANA Verrill, sp. nov. 



Plate xxjv, figures i, 2, 4; plate xxxv, figure ij plate txv, figure 2; plate 

 -j|f LXXVIH, figures i-ie (pedicellariae) ; plate LJfxtrx, figures 3-3*: (spines and 

 pedicellariae) ; plate.ax, figures 2-2& (structure). 



The type of this species is a rather large specimen collected at 

 Yakutat, Alaska, by Prof. W. R. Coe, on the Harriman Expedition. 



