31 
tangular aperture formed by the truncated ends of the joints of the pelvis, at the 
bottom of the funnel-shaped abdominal cavity, we observe the entrance to the 
alimentary canal, protected by the sphincter muscle of the superior enlarged 
columnar joint. 
To the general idea thus obtained of the organization of this animal, it 
should be added that the appearances presently to be stated indicate two other 
important particulars; Firsr, that the upper-part of the funnel-shaped cavity 
containing the viscera, was protected externally by series of small plates leaving 
a central opening for the mouths, and sECONDLY, the existence of lateral open- 
ing on the exterior of the circumference of the body, possibly forming the 
mouths of the ovaries. ‘The appearances leading to this conclusion are, viz.— 
We often trace several nearly wedge-shaped four, five, or six-cornered plates 
(PL. 111. fig 2.—P. 6. fig. 2. @.) interposed between the angles of the two second 
costals, scapule, and first and second arm joints, in a line with the lateral surfaces 
of the scapule; and in this part sometimes forming two series. These I con- 
sider as analagous to the pectoral plates of the pentacrinites, actinocrinites, &c. 
and thence conclude that this animal had also an external integument over 
its abdominal cavity, rendered stronger by the interposition of numerous 
minute adhering plates, which also spread over the excavated or channelled 
portion of the arm joints, finger joints, and tentacula, as is the case in Pen- 
TACRINUS CAPUT MEDUS#, in treating of which this structure will more fully be 
explained. That the abdominal cavity had, in this animal, really such a cover- 
ing, is rendered further probable by the occurrence of round balls of clay rest- 
ing sometimes within it, and evidently formed as casts in its interior; (which 
are erroneously noticed by Townsenp in character of Moses, vol. r. p. 269, 
as opercula) of these the upper surface seems to have moulded against some 
such covering. 
I shall now state the appearances, which I think, may possibly be econsi- 
dered as indicating the mouths of the ovaries of this animal. In or between 
the lateral surfaces of the joints of the pelvis and the insertion of the first costal 
joints, we may frequently trace a violent contraction, rendering this part of the 
animal subpentangular (PL. vit. fig. 12.) and in thesame parts we also observe 
more or less elevated tubercles, (Px. vii. fig. 7.11.12. 13 ) having a central per- 
foration, which in one instance I have traced (fig. 7.) to pass through the joint of 
the pelvis into the space between it and the costal joints, extending perhaps 
