REPORT ON THE ASTEROIDEA. 285 
is situated nearer the margin than the centre of the disk, at the top of the lateral wall in the 
interbrachial arc, and is surrounded by the spinelets borne on the adjacent abactinal plates. 
No pedicellarie of any kind are present. 
The ambulacral tube-feet have large fleshy disks. 
Colour in alcohol, an ashy grey. 
Locality.—Station 156. In the neighbourhood of the pack ice, near the Antarctic 
Circle. February 26, 1874. Lat. 62° 26’ 0” S.; long. 95° 44’ 0” E, Depth 1975 
fathoms. Diatom ooze. Bottom temperature 32°1° Fahr. ; surface temperature 37°2° Fahr. 
Genus Gnathaster, n. gen. 
It is not without great reluctance that I have proposed a new generic name for the 
present small group of species. I had hoped in the first instance to have limited the term 
Astrogonium in such a way as to have served for their reception, since all the species 
except the new ones have at various times been ranked in that genus. Unfortunately, 
however, they do not comprise a single species referred by Miiller and Troschel to their 
genus ; and on carefully studying the diagnosis given in the System der Asteriden 
(p. 52) it will be seen that that diagnosis could in no way be amended so as to admit of 
the reception of the forms now under consideration, without such a radical alteration as 
would really take away from it the only characters upon which its original recognition 
depended. 
On referring to the series of species grouped by Miiller and Troschel in the genus 
Astrogonium, it will be apparent that all of them, excepting the form originally described 
by Gray’ under the name of Pentagonaster pulchellus, are referrible to the older genera 
Pentagonaster of Linck and Hippasteria of Gray. It is therefore to this form, Penta- 
gonaster pulchellus, Gray, and its subsequently described allies, that the generic appella- 
tion of Astrogonium should now be applied, if the name is retained at all. 
Perrier * has recently expressed the opinion that this type (Pentagonaster pulchellus, 
Gray), together with a small assemblage of allied species, is worthy of independent generic 
recognition. This view appears to me just, and based on the presence of characters the 
morphological significance of which had hitherto been overlooked. As a generic name 
for this group, Perrier has restored that of Stephanaster of Ayres,’ on the ground that 
Stephanaster elegans, Ayres, is synonymous with Pentagonaster pulchellus, Gray, or in 
other words, that the form described by Gray in 1840, under the name of Pentagonaster 
pulchellus, was redescribed by Ayres in 1851 under the name of Stephanaster elegans, on 
the supposition that it was a genus and species new to science. 
With this selection of a name for the group in question I am unable to agree, for in 
* Ann. and Mag. Nat. Hist., 1840, vol. vi. p. 280. 
2 Ann. Sci. Nat. (Zool.), 1885, t. xix., Art. No. 8, p. 30. 
* Proc. Boston Soc. Nat. Hist., 1851, vol. iv. p. 118. 
