REPORT ON THE ASTEROIDEA. 561 
This large and widely distributed genus was subjected a few years ago to a critical 
revision by Professor F. Jeffrey Bell," who carefully investigated the claims of the large 
number of forms referred to Asterias to be ranked as distinct species. All workers at the 
group owe a debt of gratitude to the author of this admirable and useful memoir. Pro- 
fessor Bell divided the genus into artificial sections, and systematised the recognised species 
by means of easily observed characters, which will afford great help in the determination 
of specimens. 
The number and the great variety of the species of Asterias make the genus a very 
difficult one to deal with, and its subdivision into natural groups has been a long felt 
desideratum. Professor Bell’s scheme is, however, essentially a systematic key, mainly 
artificial in character, rather than a natural arrangement by affinities; it not unfre- 
quently results that species which are nearly related, and present a close similarity of 
habit, are widely separated and placed in sections wherein they stand isolated. For a table 
of specific differences, this perhaps may in some cases be an advantage, though it is 
decidedly unnatural from a taxonomic point of view. 
Whilst fully recognising the excellence and utility of Bell’s classification, I venture to 
think that the two methods—the artificial and the natural—may advantageously be com- 
bined, and for the species with which the present Report is concerned, I have formulated 
a scheme which seems to fulfil these requirements. To discuss the partition of all the 
species of Asterzas would demand more space than I should be justified in occupying in this 
place, and would introduce too large an amount of matter foreion to the Challenger Report. 
The groups or alliances of species which I have proposed, may, in my opinion, be 
regarded as of subgeneric rank. I further believe that some of them may ultimately stand 
as independent genera, but until more is known of the special anatomy of the species, I 
refrain from so classifying them, 
Synopsis of the Species of Asterias herein mentioned. 
A. Asterias rubens group: Abactinal spinelets numerous, but not arranged in 
definite order, usually small and often more or less grouped. Papule 
numerous, in groups : é : 5 : : : : . ASTERIAS. 
a. Heteractinid: Having six rays. 
a, Diplacanthid: Armature of the adambulacral plates consist- 
ing of two spines, 
«. Rays long and tapering, spinulation characteristically 
vesiculated. No spinelets between the parambul- 
acral series of papulz ; : : 5 vesiculosa. 
8. Rays much shorter and less tapering. Spinulation not 
specially vesiculated. Occasional spinelets between 
the parambulacral series of papule 2 : : : meridionalis, 
1 Proc. Zool. Soc. Lond., 1881, pp. 492-515. 
(ZOOL. CHALL. EXP.—PaRT LI.—1888.) ral 
