58 



The FIRST COSTAL JOINTS (PL. n. fig. 2. 9. to 14.) are externally more mus- 

 cular, reaching downwards over a greater number of columnar joints, and 

 tapering to a 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. (PL. n. 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 SECOND COSTAL (PL. n. fig. 3.) the scapula? (PL. n. fig. 4. the JOINTS 

 of THE ARMS (PL. ii. fig. 5.) HANDS and FINGERS (PL. n. fig. 6.) are formed in a 

 similar manner to those of P. Caput Medusae. 



The number of FINGERS in the smallest and youngest specimens f PL. i. fig. Q.) 

 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. TOBIN'S specimen, a certain immaturity. I have traced the increase of 

 the number of fingers to five and eight, arid ascertained that in full grown spe- 

 cimens the number amounts to sixteen, when each hand was about six inches 

 long. (PL. i. fig. 1. 



After a careful examination, I succeeded in detecting traces of the PLATED 

 INTEGUMENT covering the viscera, between the costal joints, (PL. n. fig. 8.) 

 and scapulae, as also where it covers the channel of the tentacnla. I was 

 much gratified when, on a subsequent examination of Mr. PAKKINSON'S plate, 

 (T. xvin. 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 scapulfe. 



Sections of the first Costals (PL. 11. fig. 14.) frequently demonstrate a 

 gradual increase from external laminae, 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 Medusa?. 



