398 THE VOYAGE OF H.M.S CHALLENGER. 
2. Papular areas confluent laterally. Madre- 
poriform body large and compound . : é Pharia. 
ii, Abactinal and marginal plates (in fact the whole test) 
covered with a thick membranous investment 3 : Leiaster. 
8. Abactinal plates not forming regular longitudinal series. 
i. Adambulacral armature granuliform, two or three 
series. No papule on the actinal surface, Abac- 
tinal plates comparatively small. 
1. Rays more or less cylindrical. Papule in 
areas irregularly distributed amongst the 
abactinal plates ¢ . 5 
2. Rays trigonal. Papule in one or two con- 
tinuous uninterrupted rows on each side 
of the ray : : : : 2 : ; Phataria. 
il, Adambulacral armature papilliform or spiniform, 
subprismatic, usually in three series. Abactinal 
plates comparatively large. 
1. Rays rounded. Papule on the actinal 
surface. Papule in areas : 4 : 2 Nardoa. 
2. Body pyramidal, rays triangular in section. 
No papule on the actinal surface. Papule 
; P Linckia. 
single, isolated : 2 ; Nareissia, 
b. Abactinal and marginal plates covered with membrane, the former and 
occasionally the latter bearing isolated skin-covered spinelets . . Merropiring. 
a. Asingle genus . . . . > . 0 : c Metrodira. 
Subfamily CuarTasterin®, Sladen, 1888. 
Genus Chetaster, Miiller and 'Troschel. 
Chuetaster, Miiller and Troschel, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, April 1840, p. 103. 
4 Astropus (subgen.), Gray, Ann. and Mag. Nat. Hist., Nov. 1840, vol. vi. p. 182. 
Nepanthia (pars), Gray, Ann. and Mag. Nat. Hist., Dec. 1840, vol. vi. p. 287. 
This singular genus was originally ranked with the Astropectinide, but was removed 
by Viguier’ in 1878 to the Linckiide. The justice of this step has recently been recog- 
nised by Perrier.’ I fully concur in this, although I regard Chextaster as a very abnormal 
member of the family, and have placed it in a distinct subfamily. 
Chorology of the Genus Cheetaster. 
a. Geographical distribution :-— 
ATLANTIC : Two species between the parallels of 10° and 40° N. 
Chetaster longipes, from the Mediterranean, and off the Azores 
and Bermuda. Chetaster nodosus, from Guadeloupe. 
1 Archives de Zool. expér., 1878, t. vii. p. 147.’ 
* Nouv. Archives Mus, Hist. Wat., 2e Serié, 1884, t. vi. p. 164. 
