on the Genus Solaster. 441 
Thus the paxille in Solaster glacialis stand further apart 
and are a little longer than in S. endeca, but neither so long 
nor so wide apart as in S. papposus ; along the margin of the 
arms there is a series of pretty large penicilliform paxille, 
which are seen most distinctly from the dorsal side, as in S. 
papposus, but without projecting so strongly as in that species, 
while the transverse rows of paxille which are so characteristic 
of the ventral surface in S. endeca are far from being so promi- 
nent in S. glacialis. And with regard to the dermal skele- 
ton, we find that the small calcareous pieces which form the 
net have much agreement in form and distribution with those 
of S. endeca, although they most resemble those of S. furcifer, 
which the species exactly resembles in the form and arrange- 
ment of the marginal plates. We think therefore that Solase 
ter glacialis shows the utter untenability of the above-men- 
tioned division of the genus Solaster. 
Finally, we shall now take into consideration the genus 
Lophaster, recently proposed by Prof. Verrill for Solaster 
furcifer, Diib. & Kor. 
To justify the establishment of this genus Prof. Verrill ex- 
presses himself as follows :—‘‘ This species differs so widely 
from Solaster in the structure of the skeleton and the small 
development of the disk as to require the establishment of a 
new genus for this type. It is specially distinguished by 
the highly developed skeleton of the underside, differen- 
tiated marginal plates, and prominently reticulated dorsal 
plates” *. Professor Jeffrey Bell is rather inclined to admit 
that the genus Lophaster is well founded, laying great stress 
especially upon the “ differentiated marginal plates, one dorso- 
marginal and one ventro-marginal.” We have already ad- 
mitted that the marginal plates play an important part in 
characterizing genera, although we are unable to recognize 
them as decisive. Verrill says that Solaster furcifer differs so 
remarkably from the genus Solaster in the structure of the 
skeleton and in the small development of the disk that a new 
genus must be formed for it; it is principally the strongly 
developed skeleton of the ventral surface, the differentiated 
marginal plates, and the strikingly reticulated dorsal plates 
that determine the formation of the new genus. 
Now with regard to the size of the disk in proportion to the 
arms, this varies very considerably, and is only of slight im- 
portance in generic determinations; but it is otherwise with 
the structure of the skeleton. We shall first refer to the der- 
mal skeleton. 
* ‘Notice of recent Additions to the Marine Fauna of North America,” 
by A. E, Vervill (Amer. Journ. Sci. ser. 3, vol. xvi. p. 214). 
