LEPTOPTYCHASTHR. 65 
Distribution. Both sides of the northern part of the Atlantic, and 
Arctic Ocean, 7-632 fms. 
a. Faeroe Channel, 60° 0' 0" N., 5° 18' 0” W., 312 fms. ‘Porcupine’ Exp. 
ASTROPECTINID (see p. 20). 
ASTROPECTININ A (see p. 20). 
Key to the Genera of Astropectinine. 
A. Superomarginal plates with a prominent 
ridge. 
Superomarginals much smaller than infero- [p. 65. 
WIRGECMINIERES a ietaisla s aiesaid sw elle e o'er e clea 1, LEPTOPTYCHASTER, 
Superomarginals nearly or quite equal to 
MOE OM AT PUTEAIG | Jo, ara ws o,0\s:o ein ersins wie’s 2, ASTROPECTEN, p. 66. 
B. No prominent ridge to superomarginals. 
Spinelets simple; ambulacral armature a 
straight series of numerous and uniform 
S(IOGIE USS lee aie SR a ae ae 3. PsILASTER, p. 68. 
Spinelets in sheath; ambulacral armature 
an angulated series of a few spinelets, [p. 69. 
GEE ARLE IDREL plete eieice wens ches sis ee ses 4. BATHYBIASTER, 
1. LEPTOPTYCHASTER. 
Leptychaster, Srhith, Ann. § Mag. xvii. (1876) p. 110. 
Leptoptychaster, id. Phil. Trans. elxviii. (1879) p. 277; Slad. Chall. 
Rep. Ast. (1889) p. 175. 
Flattened, with narrow ambulacra; superomarginals smaller than 
inferomarginals, intermediate plates extending only partly along 
the rays. 
1. Leptoptychaster arcticus. 
Astropecten arcticus, MZ. Sars, Nyt Mag. vi. (1851) p. 161; td. Faun. 
litt. Norv. ii. (1856) p. 61, pl. ix. figs. 16-18; id. Norg. Ech. 
(1861) p. 32; Duj. § Hup. Echin. (1862) p. 428. 
Archaster liitkeni, Barrett, Ann. § Mag. xx. (1857) p. 46, pl. iv. 
fig. 3; Duy. § Hup. Echin. (1862) p. 428. 
Archaster arcticus, Verr. Am. J. Sci. xvi. (1878) p.373; Storm, Vid. 
Norsk. Selsk. Skrif. Throndjhem, viii. (1879) p. 252. 
Leptoptychaster arcticus, Sladen, Chall. Rep. Ast. (1889) p. 189. 
R= 9°25 Tr 
A small species, with a large disk and rapidly tapering arms, the 
angles between which are distinctly rounded; the rather narrow 
ambulacra are bounded by a row of long spines arranged by threes 
on each adambulacral, outside of which are other rows so closely 
packed as to be almost disorderly in their disposition; the inter- 
mediate plates which fill up the rather large interbrachial area, but 
P 
