gg BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



c'. Abactinal platea lobed; marginals broader, covered with compact, rigid, polygonal granules 

 (guperomarginaU) and squamae (inferomarginals); superomarginals with one or two tubercles; 

 adambulacral furrow spines compressed with broad side to furrow; actinal intermediate platea 



covered with squaraiform spineleta •_ borealis, p. 91 . 



c*. Abactinal plates not lobed; marginals narrower, the Buperomarginals without tubercles and 

 covered with delicate capillary splneleta; inferomarginals with delicate imbricating narrow 

 squamiform spinelets; adambulacral furrow spines strongly compressed with edge to furrow; 



actinal intormodiutc platea with slender spinelets Isetmophilus, p. 95. 



a'. Inferomarginals entirely without npecialized spines; border of ray even, not serrate from the form of 

 inferomarginals; papuhe absent from center of disk; madreporic plate median sized, hidden, but 

 with only one or two paxilhe on its surface anoplus, p. 97. 



DIPSACASTER EXIMIUS Fisher. 

 PI. 11, figs. 1, 2; pi. 13, fig. 2; pi. 14, fig. 1; pi. 16, fig. 3; pi. 52, figs. 1, la-c. 

 Dipiacaater eximius Fisher, Bull. Bur. FLsheries for 1904, vol. 24, June 10, 1905, p. 296; Zool. 

 Anz., vol. 35, March 29, 1910, p. 546. 



Diagnosis."— Rays five. R = 124 mm.; r = 55 mm.; R = 2.26 r. Breadth of 

 ray at base, 60 to (55 mm.; at middle of ray, 46 mm. General form flattened, rays 

 broad, leaf-lil^e in sliape, tapering gradually, but with an outwardly curved contour; 

 extremity bluntly pointed; interbrachial angles wide, abruptly rounded; abactinal 

 surface but slightly inflated, a slight depression on interradial lines; actinal surface 

 subplanc. Abactinal paxilla? very regularly arranged in chevrons, largest along 

 mitlradial area and center of disk; each with a large tuft of very numerous slender 

 spinelets which extend down pedicel for half its length, or more ; regular arrangement 

 interrupted on area of largest paxillie. Papulte generally distributed, six around 

 each lobed plate, except along radial line where there are two or three papulae to 

 each area, and twelve to twenty about many of the plates. Marginal plates massive, 

 the inferomarginals defining contour of ray, and armed on outer end with a trans- 

 verse or vertical row of four to six short stout tubercles; superomajginals usually 

 with a single short tubercle; occasionalh^ more. Adambulacral plates with five or 

 six strong furrow spines, the median longest and all more or less compressed, with 

 edge uppermost; and on actinal surface two or tliree rows of three or four spinelets 

 each; usually only the inner actinal row has any regularity. Actinal intermediate 

 areas large, and maintaining a considerable breadth far along ray; intermediate 

 plates strongly carinated bearing a cluster of spinelets of which the peripheral are 

 slenderest, those in center not typically much enlarged although occasionally so on 

 some specimens. 



Description. — The rays in this species have in large examples, a very character- 

 istic broad leaf-shape. That is, they taper only slightly from base to outer third, 

 thence the edges curve and taper rapidly to the blunt extremity. Paxillaj large; 

 largest in center of disk and along median radial areas, thence decreasing gradually 

 and uniformly in size toward the marginal plates. They are very regularly arranged 

 m oblique transverse rows along either side of the median radial area, forming 

 chevrons pointing toward center of disk; but on latter area and along radial line the 

 paxillie, due to their becoming larger, have no regular arrangement. Opposite or 

 corresponding to first four superomarginals, in large specimens, are eight to ten 

 transverse rows of paxilla?. Each paxilla springs from a lobed plate (described 



a From a large apecimen from station 3112. 



