324 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



and its relationship witli australis is greatly in need of elucidation. If regularis is 

 only a variunt of australis, the remarks made above concerning the differences 

 between australis and borealis will have to be emended. Sladen refrains from 

 stating how many specimens he had (a defect of practically all his descriptions), so 

 that it is not possible to jutlge of the range of variation. Regularis has only eight 

 rays, wliich are unusually long (R = 4.5 to 5 r), broad stumpy paxillie with six to 

 ten spinelcts, less markedly compressed marginal plates, with more numerous and 

 ajjparcntly shorter spines, less prominent actinal adambulacral spines (four or 

 five in number), and a row of five suboral spines. 



SOLASTER HYPOTHRISSUS Fisher. 

 PI. 9S, figs. 1, 2; pi. 113, figs. 5, 5a. 

 Solaster hypothrissvs Fisher, Zool. Anz., vol. 35, March 29, 1910, p. 574. 



Diagnosis. — Similar in general appearance and structure to S. borealis, but 

 differing in having a row of five to seven prominent suboral spines parallel to the 

 median suture, in having a maximum of six long subambulacral spines, instead 

 of four or less, and in having the abactinal pseudopaxillaa slightly higher with seven 

 to nine spinelets which are blunter than in typical borealis and end in several points, 

 not in an attenuate denticulate tip. Rays ten. R = 118 mm.; r = 38 mm.; 

 R = :5 r + . 



Description. — It is not possible to determine whether this is a distinct species 

 or a "form" of borealis. A close examination reveals many points of intimate 

 resemblance to borealis, but no intermediate specimens have been found. The 

 chief features have been alluded to in the diagnosis. The papulee are prominent, 

 as in borealis, but the paxillse are stouter with more spinelets (seven to nine instead 

 of three or four). The spinelets are less attenuate distally and form a rosette 

 with one in the center. There are about thirty marginal plates not differing in 

 any important respects from those of borealis. The actinal intermediate plates 

 extend in a single series nearly to end of ray; distalh' they are very inconspicuous. 

 The adambulacral armature is very bristling, the actinal series containing proxi- 

 mally six spines, the outer the shortest, and distally five, then four. The furrow 

 series has only three to five spinelets, five proximally, which are webbed for about 

 hidf their length. They do not differ in important respects from those of borealis, 

 but are slightly longer. The mouth plates and their armature depart more widely 

 from those of borealis, having a bristling array of suboral spines five to seven in a 

 row parallel with and close to the suture. The innermost spine is the stoutest 

 and about as long as the longest actinal spine of the first few adambulacral plates. 

 The marginal spines are rather longer than in borealis, especiallv the outer ones. 



Type.—Cni. No. 27787, U.S.N.M. 



Type-locality. — Station 3338, south of the Shumagin Islands, Alaska, 625 

 fath(mis, green mud, two specimens. 



Distribution. — Vicinity of the Aleutian Islands. 



Specimens examined. — The tji>es and one specimen from station 4784, near 

 Attu Island, 135 fathoms, coarse pebbles. 



