222 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



on the distal plates of the large specimen of jordani ; the other speci- 

 mens have 2 or 3 enlarged spines proximally and 1 to 3 distally. 



All the specimens but those from station 5582 have a variable 

 number of post-adambulacral fasciolar pedicellariae or pectinate 

 fascioles. These were not well pronounced in the type. 



In conclusion it may be stated that the relationship of Ps. mozaicus 

 to Ps. jordani is not at all clear. If the specimens collected by the 

 Albatross are really all of one species they indicate that the two 

 forms approach much closer than heretofore supposed. 



PSEUDARCHASTER OLIGOPORUS Fisher. 



Plate 59, fig. 1 ; plate 60, fig. 3 ; plate 91, figs. 2, 2a. 



Pseudarchaster oligoporus Fishee, 1913a, p. 625. 



Diagnosis. — Most nearly resembling Ps. pectinifer Ludwig and 

 Ps. dissonus Fisher. E=87 mm., r=21 mm.. E=4.1 r; breadth of 

 ray at base, 24 mm.; rays slender, long, and very attenuate at the 

 extremity; side of ray low, rounded; marginal plates small, espe- 

 cially distalh', where the superomarginals are confined to side wall 

 of ray and are longer than wide, square, or slightly wider than long; 

 papular area restricted to center of disk, and petaloid radial areas 

 extending about one-fourth the length of ray ; abactinal plates tabu- 

 late on papular area, the roundish tabula low, spaced, and bearing 

 20 to 30 polygonal granules ; outside of papular area plates elliptical 

 or oblong, arranged in oblique transverse series and with very low 

 tabulum, or distally none; superomarginal plates with coarse, spaced, 

 covered granules; inferomarginals with pointed, conical, appressed 

 .spinelets, and proximally 8 to 12 appressed sharp spines in a zigzag 

 transverse series, these becoming reduced to 1 or 2 toward the ex- 

 tremity of ray ; actinal intermediate plates in 5 chevrons, the series 

 adjacent to adambulacrals extending to tenth or eleventh infero- 

 marginal, each plate armed with 1 to 3 tapering, sharp spines, and 

 5 to 20 short, sharp, spaced peripheral spinelets; a variable number 

 of plates adjacent to adambulacrals with the transverse sutures armed 

 with fasciolate pectinate pedicellariae, the spinelets being short and 

 broad tipped; furrow series angular with 8 or 9 short, sometimes 

 slightly compressed, blunt, or bluntly pointed spines, and 1 or 2 

 tapering, pointed subambulacral spines, surrounded by 5 to 10 

 shorter, spaced, pointed spinelets. 



Description. — Abactinal plates medium-sized, not at all compactly 

 placed, but distinctly spaced. The papular area is relatively small, 

 being confined to the center of disk and 5 petaloid radial areas ex- 

 tending two-fifths R, or one-fourth the length of ray. Here the 

 plates are tabulate, the paxillar crowns being roundish and spaced, 

 and arranged in longitudinal and oblique transverse series, the plates 



