92 ASTEROIDEA. 
Slad. Echinod. Arctic Sea, (1881) p. 48; Sladen, Chall. Rep. Ast. 
(1889) p. 459. 4 
Chetaster borealis (n.n.), Diiben, Ofv. Svensk. Ak. Forh, 1844 (1845), 
ots, 
fi R = 3r (nearly). 
Arms five ; spines in delicate tufts, rather widely spread or rather 
coarser and more closely packed; arms wide and flat; the marginals 
of both series with an elongated pedicle; three or four spines on 
each adambulacral plate. Colour in spirit yellowish. 
Not known to grow as large as its congeners. 
Distribution. Both sides of North Atlantic; on the East not 
known south of Faeroe Channel; on the West as far south as the 
Gulf of Maine. To 605 fathoms. 
a. Faeroe Channel, 384 fms. ‘Porcupine’ Exp. 
CORETHRASTERID& (see p. 23). 
CORETHRASTER. 
Korethraster, Wyv. Thoms. Depths of the Sea, (1873) p. 120 (n. n., but 
Jig. of K. hispidus, sp. n.); Dan. § Kor. op. cit. p. 95; (?) Perr. Nouv. 
Arch, Mus. vi. (1884) p. 211; Slad. Chall. Ast. (1889) p. 462. 
Corethraster, v. Marenz. Denkschr. Ak. Wien, xxxv. (1878) p. 383. 
1. Corethraster hispidus. 
Corethraster hispidus, Wyv. Thoms. Depths of the Sea, (1873) p. 120, 
fig. 15; v. Marenz. Denkschr. Ak. Wien, xxxv. (1878) p. 383; 
Dan, §& Kor, Norske Nordhavs Ast. (1884) p. 95, pl. xii.; Sladen, 
Chall. Rep. Ast. (1889) p. 464, pl. xxx. figs. 6-9, 
Body thick ; rays in young twice, in older forms four times as 
long as radius of disk. Spines very long, arranged in tufts of 6-10, 
which are united at their base. Adambulacral spines in two rows, 
flat and hollow. Pale yellow. 
Measurements of single British specimen :— 
R=8°5, r=4'5; height =4; spines =2 mm. 
Distribution. Northern Atlantic. So far as is known from the 
eastern side only. The species spoken of by Mr. Whiteaves (Ann. & 
Mag. x. (1872) p. 346) is, as he informs me, Pteraster militaris, 
and not, as might be supposed, Corethraster hispidus. 101-632 fms. 
a. Faeroe Channel, 60° 14’ N., 6° 17' W., 632 fms. ‘Porcupine’ Exp, 
PTERASTERIDZE (see p. 23). 
Key to the Genera of Pterasteridee. 
a. Adambulacral spines in transverse combs ; 
spines united by a web.............+-.. 1, PTERASTER, p. 93. 
6, Adambulacral spines not forming transverse 
combs; spines not united by a web...... 2, HYMENASTER, p. 94. 
