REPORT ON THE ASTEROIDEA. 225 
character referred to has subsequently been called in question. Sars? states definitely 
that it did not occur in any of his specimens, and he considered that Diiben and Koren 
had been deceived by the presence of foreign matter. Diiben and Koren remark that 
the character is not a constant one. 
A large series of specimens shows a considerable amount of variation in the relative 
breadth of the supero-marginal plates and the paxillar area upon the rays. In examples 
from Drobach the supero-marginal plates as a rule arch over very slightly upon the actinal 
surface. On the other hand, in a specimen from Tromsé in the Christiania Museum they 
are very wide. This example is also noteworthy on account of the different character of 
the paxille, which are more rounded in form, and with the component spinelets radiat- 
ing more apart ; whereas in the usual type the spinelets are pressed together and directed 
upward, and the crown is more or less pentagonal in form. The spinelets on the aboral 
margin of the infero-marginal plates of the Tromsé specimen are very insignificant, and 
are almost aborted into robust squamules. The armature of the adambulacral and actinal 
intermediate plates, which is papilliform, uniform, and invested with membrane, has a 
very distinct appearance, as well as the almost naked and flatly appressed covering of the 
infero-marginal plates. In the Drgbach specimens the three or four spines on the infero- 
marginal plates are well developed. 
I have also seen a specimen from Lofoten with broad supero-marginal plates and well- 
developed spines on the infero-marginal plates, which are rather wide apart and uniform. 
A number of the specimens in the Stockholm collection have the supero-marginal plates 
arching well upon the abactinal surface, but in an example from Bohusliin the arching is 
very slight. 
To a certain extent the supero-marginal plates appear to be relatively broader in young 
forms, and narrower and less arching in the larger examples. 
The most interesting variety I have seen is one in Christiania determined by M. Sars, 
which bears a ticket inscribed by him, “ Varietet med bredere Paxillarfeldt paa Armene og 
mindre brede dorsale Randplader. Paa 200 Favnes Dyb paa Line. Fensfjorden.” In this 
example the supero-marginal plates are very narrow and almost perpendicular. The spines 
on the infero-marginal plates (a series of three to five) are long and thin, the third from the 
margin being longest. The central part of the plateisnaked. Similarly the supero-marginal 
plates have only a few granules on the upper part and near the margins of the plate. 
Sars’ has remarked that the northern examples of this species seem to have generally 
shorter arms than the southern ones. 
2. Psilaster acuminatus, n. sp. (Pl. XL. figs. 1 and 2; Pl. XLII. figs. 7 and 8). 
Rays five R=65 mm.; r=15 mm. R=43 7. Breadth of a ray at the base, 
14°5 mm. 
1 Oversigt af Norges Echinodermer, Christiania, 1861, p. 31. 
(zooL. CHALL. EXP.—PaRT LI.—1888.) 29 
