REPORT ON THE ASTEROIDEA. 235 
from the infero-marginal plates. All these actinal intermediate plates bear uniform 
squamule-like papilla invested with membranous sacs. 
Adambulacral plates large and pentagonal in shape. Armature consisting of :—(1.) 
An angulated furrow series of five short, subequal, papilliform spinelets, the median one 
being triangular in section. (2.) On the actinal surface two longitudinal series of short, 
flattened spinelets, the inner series often disposed in such a manner as to close against the 
furrow series, thus forming perhaps an incipient pedicellarian apparatus. All the spinelets 
are in membranous sheaths. 
Madreporiform body small, oval, and situated about its own diameter distant from the 
margin of the paxillar area. 
No pedicellarize are present. 
Remarks.—This genus is distinguished from Bathybiaster by the presence of the 
epiproctal cone, and by the absence of the pedicellarize which specially characterise the 
latter form. 
The genus I/yaster, established by Danielssen and Koren’ for the reception of a small 
Asterid furnished with a remarkably developed epiproctal prolongation, dredged during 
the Norwegian North Atlantic Expedition, is probably more nearly related to this genus 
than to any other form with which we are acquainted. So far as ] am able to judge from 
the description and figures alone, the position of Jlyaster in the tabular scheme of the 
family would probably be adjacent to Phoxaster, and perhaps intermediate between that 
genus and Bathybiaster. It differs from Phowaster by the extraordinary development of 
the “dorsal appendage” and by the character of the armature of the adambulacral plates ; 
furthermore, as no mention is made in the careful description given by its authors of any 
special membranous investment of the general tesumentary spinulation or granulation, 
Ilyaster probably differs in that respect also. 
Respecting the dorsal appendage, it may be remarked that the difference in the relative 
size of that structure in J/yaster and Phoxaster is not greater than that existing between 
different species belonging to the genus Porcellanaster; for instance, between Porcel- 
lanaster ceruleus and Porcellanaster caulifer. The structure of the prolongation, 
however, would appear to be much more specialised in I/yaster than in Phowxaster. I 
fully share with the learned describers of J/yaster their doubt as to its being an adult 
form. 
I have on a preceding page (pp. 131, 132) stated my opinion that this elongate 
epiproctal prolongation is in no way homologous to the stem of a Crinoid, as maintained 
by Drs Danielssen and Koren.” 
1 Nyt Mag. f. Naturvidensk., Bd. xxviii, Iste Hefte, p. 4, tab. i. 11. figs. 15-19; Den Norske Nordhavs- 
Expedition, 1876-78, Zoologi, xi. Asteroidea, 1884, p. 100, tab. vii. figs. 15-19. 
2 Loe. cit., pp. 102, 103. 
