102 
a 
A small Cuavicutar Jorxt inserted between the two hands proceeding 
from one scapula, separates the integument and vessels under it in their pro- 
gress upwards, (Pt, 11. fig. 5.) 
Capitat Prates.— (Pt. tv. fig. 30. to 39.)\—The plates forming the upper 
part of the integument over the abdominal cavity, Ihave named capital plates ; 
they have like the pectoral plates different angles, but are covered by a thicker 
muscle, which is connected (although only slightly so, as appears from the 
pectoral plates not exhibiting those folds which result from strong nmscular 
action) with those proceeding from the pelvis over the first costals, and laterally 
extending upwards over the intercostals and pectorals. It receives a new 
impulse from a sphincter-like muscle placed in the centre, which is capable 
of forcing up the margin of the mouth into an elongated and protruding 
proboscis, and at the same time contracting the area between the arms, 
and thereby enabled to pull these up, and bring the hands and _ fingers 
together ia a close fasciculus. Meanwhile the muscle or portion of muscle 
covering each capital plate, is also able by its contraction to draw up 
in the centre, and thereby to form a more or less elongated tubercle, whose office 
it probably is to push on the food to the mouth, so that the whole integument 
thus assumes an echinated appearance. When the contractile force is most 
strongly exhibited, the proboscis also becomes studded with similar tubercles 
(Pu. u. fig. 1. and 2.) but otherwise those tubercles are exhibited only on the 
capital plates more remote from the centre, those near the proboscis remain- 
ing smooth. (Pt. 11. fig. 6. and 7.) On the relaxation of the muscles these 
tubercles disappeat—the proboscis gradually subsides—the space between the 
arms widen—and the fingers are permitted to expand. Specimens in every 
state of contraction occur ina fossil state, and most distinctly prove that the 
markings and appearances described, can be ascribed only to muscular action, 
