449 On the Genus Solaster. 
The dermal skeleton of the dorsal surface in Solaster fur- 
cifer consists of a tolerably closely reticulated calcareous net, 
produced by small cross- or X-shaped calcareous plates laying 
their branches upon one another ; between the meshes we see 
one or more tentacular pores, according as the meshes are 
large or small. We find almost the same arrangement in 
Solaster endeca, but still more strikingly in S. glacialis, in 
which the only difference is that the individual calcareous 
pieces are somewhat larger and have rather shorter branches, 
by which means the meshes are rather smaller than in 8S. 
Surctfer. 
The dermal skeleton of the ventral surface, which is parti- 
cularly prominent in the interbrachial spaces, should, accord- 
ing to Verrill, be more highly developed in Solasier furcifer ; 
but in this we cannot agree with him. The calcareous plates 
of the ventral surface in S. furcifer are more or less cruci- 
form, with short arms, which certainly lie in an imbricated 
fashion upon each other, but which nevertheless leave small 
vacant spaces; while the calcareous plates in S. glacialis, 
which are nearly cruciform, and in 8S. endeca, where they are 
more oval, are closely imbricated. 
The odontophores in Solaster furcifer do not differ from 
those of the other species ; they have the typical form of the 
genus Solaster. 
The marginal plates are placed in two series, the one be- 
longing to the dorsal, the other to the ventral surface. 
The dorsal. marginal plates are small, somewhat oval, thin 
plates which lie upon the innermost part of the arms a little 
apart, but approach each other more and more as they advance 
towards the end, until they come together completely. They 
have upon the upper surface a small depression which serves 
as an articulating surface for the dorsal series of paxille along 
the margin, while the lower surface is smooth and rests upon 
a small part of the corresponding ventral marginal plate, united 
to it by strong ligamentous tissue. 
The ventral marginal plates are a little more oblong and. 
rather larger than the dorsal; their lower surface, besides 
_ attaching itself by a small part to the dorsal marginal plate, 
furnishes articular surfaces for the ventral series of paxille; 
their upper surface is somewhat concave, and rests upon the 
rounded lower part of the corresponding adambulacral plate. 
The skeleton almost exactly resembles that of Solaster 
papposus. ‘The ambulacral plates have perhaps rather broader 
transverse processes, and the adambulacral plates are somewhat 
thinner ; but beyond these we can find no difference. 
From what has been stated it must be seen that Solaster 
