232 



BULLETIjST 100, UNITED STATES NATIONAL MUSEUM. 



Remarks. — Paragonaster ctenlyes was dredged by the Challenger 

 in the Arafura Sea between the Ki Ishmds and Banda Islands, in 

 140 fathoms, blue mud. Although no intergrading forms between 

 it and hypacanthus have been found, the very close similarity be- 

 tween the two seems to indicate a conspecific relationship. At the 

 same time, in spite of minor variations, the special characters of 

 hypacanthus are constant in mature examples, over a considerable 

 geographical area. 



PARAGONASTER STENOSTICHUS Fisher. 



Plate 60, fig. 2 ; plate 70, fig. 2 ; plate 71, fig. 1 ; plate 91, figs. 10, 10a, 

 Paragonaster stenostichus Fisher, 1913a, p. 627. 



Diagnosis. — Ditfering from P. ctenipes in having the abactinal 

 plates of slender portion of ray, narrower than long, and proxi- 

 mally narrower than the adjacent radial plat6s of disk, instead 

 of broader; in having more numerous, croAvded, and coarser central 

 granules, and slenderer peripheral granules; and in having nar- 

 rower adambulacral plates, lacking the characteristic fasciolate pedi- 

 cellaria of ctenipes.^ except in a less specialized form on the first 

 few plates. R=45 mm., r=12.5 mm., R=3.6 r; breadth of ray at 

 midinterbrachium, 14 mm.; at distal margin of fourth superomar- 

 ginal (the proximal end of the slender portion of ray), 8 mm., oi 

 length of first 5.5 superomarginals measured on ambitus. 



Description. — Abactinal area pentagonal or arcuate pentagonal; 

 abactinal plates comparatively large, all strongly tabulate and pax- 

 illiform, arranged very regularly in close-set rows parallel to the 

 radial series, and also in series proceeding obliquely from the radial 

 series to margin. Radial plates the largest, increasing slightly in 

 size distad up to the point where the adradial series end, and only 

 the ra dials separate the superomarginals. Here they become nar- 

 rower, longer than wide and continue to decrease very gradually 

 in size to the end of ray. Moreover, these plates are slightly tabu- 

 late, proximally, with a well-defined groove separating them from 



