104 
characters. A simple contraction produces on every plate a nearly pointed star- 
like figure, each ray being directed towards the sides. A partial contraction 
extends the points of the rays, and a very powerful one forms a continuation 
of the rays of the star on one plate, extending with an equal thickness to 
the adjoining plate. It is this degree of contraction which permits our tracing 
the direction which the muscles pursue in acting on the arms and capital plates, 
as may be fully seen in a fine specimen in my collection. (Pr. r. fig. 1.) 6 
divided action from the three adhering joints of the pelvis produces two folds, 
directed to the centre of the first costal plates, (resting upon the lines of their 
sutures) ; here it unites and proceeds over the second costal to the centre of the 
scapula, where the muscle divides and attaches to the first joint of each hand. 
Another fold extends laterally on each side from the centre of the first costals 
across the intercostals near it, to the first fingers of the opposite arms, each again 
dividing at the second intercostals, and sending branches to the pectoral plates. 
Other rays decisively point out lateral action. Another specimen in my col- 
lection, shows the ridges produced by contraction slightly waved, (PL. 11. fig. 3.) 
whilst a third specimen (PL. 11. fig. 4.) exhibits two or three ridges, according 
as the costals traversed by them are inserted over the suture of the pelvis, or 
over the middle of its plates, sending double folds to each of the two lateral 
angles, and producing a corrugation in the centre of the costals. 
The PEcrogAL PraTrs (Pr. rr, fig. 7. to 14.) do not contract into a simple 
tubercle, but form an elongation dividing at its summit into several points. 
The first Finger sets off from the outside of the cuneiform joints of-the arm, 
and the continuation of the hands consists of two or three series, each contain- 
ing two common and one cuneiform joint, and terminating in three or four 
fingers. 
The proboscis-like mouth, is capable of very considerable elongation, as is 
shown in the fine specimen figured by Luwyn: by the obliging kindness of the 
Rev. Professor BuckLaNnD, I have been enabled to examine and refigure 
it(PL.1.fig. 2.) with a more careful attention to those anatomical details to which 
I have particularly directed my inquiries in investigating the history of these 
animals. 

I am indebted to the polite attention of the Rev. R. HaLırax, (with whom I 
made an excursion to the Mitcheldean Limestone Basin) for several detached 
