AQ 
cimens, in which, if finely preserved, the muscular plice of the external 
integument may frequently be traced, extending over the former, this, and the 
following joints. At its inner truncated point it has an elegant lip-like pro- 
cess, similar to that noticed on the former joints, the plice of both assuming 
a perfectly conformable disposition, it has at its lower surface the transverse 
perforated ridge, which also appears to exist at its superior surface. How- 
ever, this last fact I can only advance hesitatingly on the appearance of a single 
specimen, and beg to observe, that it does not accord with the organization 
noticed in the Apiocrinites rotundus, to which I have found (speaking in general 
terms) the present species strictly conformable in this point. 
The scapula (PL. m1. fig. 9. to 11.) rest on the subconcave surfaces of the 
second costals, and being destined to support a row in which the division of 
pieces is doubled, the upper surface is formed into an angular ridge, and the 
lateral surfaces, in old specimens, are scarcely perceptible; so that in the ex- 
terior circumference the margin of each joint is nearly triangular. At the in- 
terior truncated point it is excavated, having in the centre a projecting pointed 
process, on each side of which another excavation exists, behind which the sub- 
triangular perforated ridge is placed in a slanting transverse direction. At 
the lower surface a ridge also exists of a subtriangular figure, all the 
angles are drawn in, and hence the joint has here again a convex form. The 
scapule evidently have lost all their analogy to the Apiocrinites, and point out 
clearly in their formation a transition of organization to the next genus. 
On the five scapule rest the ten first arm joints (PL. 1. 1. and 2.) two of 
them articulating to each scapula, viz. one on either slope of its superior angular 
ridge, the outer circumference of each arm joint forms a parallelogram con- 
tracted and drawn in at the angles, and hence has not unfrequently in young 
specimens a tubercular elevation. 
To the first arm joint succeed several thinner joints, externally oblong, 
straight on the lateral surfaces, and nearly flat on the upper and Jower surfaces; 
they are of a horse-shoe shape, and provided with tentacula on alternate sides. 
Their number varies from six to eight, according to the age of the individual. 
The following joints which 1 should feel inclined to call those of THE 
FINGERS (PL, 11. fig. 1.) have sloping surfaces, and thin off on the opposite 
