126 
ing through the auxiliary side arms, which vessel was perhaps surrounded by a 
cuticle possessing the qualities of a nerve and muscle; as appears very pro- 
'bable in an animal where the nerves must have been so minutely distributed. 
On examination of the conformation of the analogous parts in the Stellerida, 
itis at once proved, 
Thatin the genera Ophiura 7۶ Asteria, and Euryale, the ossicula forming the 
arms proceed from an ossicular arrangement surrounding the mouth, whereas 
in the Crinoidea the system of joints supporting the arm proceed from the base 
of the cup containing the intestines, and are only loosely connected with the 
muscle surrounding the mouth, by the plated integument covering that cup. 
In the three genera mentioned, the mouth is pentagonal, and provided with 
teeth, of which there are no traces in the Crinoidea. 
The following characters appear distinctive between the three above stated. 
genera of the Stelleridz, but still not such as to approximate any of them parti- 
cularly to the Crinoidea :— > 
In the genus Ophiura, the abdominal cavity extends beyond the mouth in 
a subglobose manner. | | 
In the Asteria, the abdominal cavity extends laterally over the ossicular 
arrangement of the arms to admit ten coeca. 
In the Euryale, the protruding semiglobular abdominal cavity is formed by 
ten plates, each two serving as a stay to an arm; thus if the arms were removed, 
these animals would exhibit by this arrangement of their plates in ten divisions, 
_and the teeth, a transition to the Echini. 
4 
In the Ophiure? Euryale, and Asterix, there exists no perforation in the 
arm joints, hence the vessel passing through it in the Crinoidea is omitted: 
or differently placed. 
: 1 
The inner lateral angles of the arms of the Asterix being provided with: 
* I here add a mark of interrogation, not having had opportunity to examine Ophiura 
sufficiently in its anatomical details, and judging therefore from delineation only. 
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