58 
The First Costar Joints (Pu. u. fig. 2. 9. to 14.) are externally more mus- 
cular, reaching downwards over a greater number of columnar joints, and 
tapering toa point. They have each a longitudinal central ridge, which is 
more clearly exhibited when in a contracted state, when also near the upper 
portion between the ridge and the pointed angles of the pelvis, a tubercle ap- 
pears on either side. (Px. 11. fig. 13.) It here suggests itself to me that the 
elongation of the first costals in the pentacrinites is intended to strengthen the 
column in this place, where being most muscular, it is most yielding, and there- 
fore requires strong abutments to bear the weight of the arms and fingers, and 
sustain their various motions. : 
The Seconp Costa (Pt. 11. fig. 3.) the scapule (PL. 1. fig. 4. the Joints 
of THE ARMS (PL. 11. fig. 5.) HANDS and FINGERS (PL. 11. fig. 6.) are formed in a 
similar manner to those of P, Caput Meduse. 
The numberof rineers in the smallest and youngest specimens (PL. 1. fig. 2. 
I have seen, amounted to four ; the length of the hands from the cuneiform arm 
joint being scarcely an inch, and of the whole animal not above two inches, 
These fingers showed, like those belonging to the reproduced arms on the late 
Mr. Toniy’s specimen, a certain immaturity. I have traced the increase of 
the number of fingers to five and eight, and ascertained that in fall grown spe- 
cimens the number amounts to sixteen, when each hand was about six inches 
long. (Pu. 1. fig. 1. 
After a careful examination, I succeeded in detecting traces of the PLatep 
INTEGUMENT covering the viscera, between the costal joints, (Pu. 11. fig. 8.) 
and scapule, as also where it covers the channel of the tentacnla. I was 
much gratified when, on a subsequent examination of Mr. Parkrnson’s plate, 
(T. xviit. fig. 2.) I found that his draughtsman (to whose talent of making faith- 
ful and correct delineations I cannot omit to give my highest testimony,) had 
also represented the plates of the integument between the costals and scapule. 
Sections of the first Costals (Px. 1. fig. 14.) frequently demonstrate a 
gradual increase from external lamine, as noticed in Apiocrinites rotundus. 
I apprehend that perfect and full grown animals of this and the following 
Species, must surpass all others in their number of joints and plates, not even 
excepting Euryale Caput Medusz. 
