138 



In each of the horse-shoe-like depressions traversed by a perforated ridge 

 atthe summit of the scapula;, is inserted the first ARM JOINT, of similar con- 

 tour to the depression, to whose superior surface adheres a CUNEIFORM JOINT, 

 (considered by Mr. MANTELL as analogous to the os humeri) and indicating 

 that the arm here divides, and sends off fingers in a manner analogous to what 

 we observe in the Crinoidea. 



The space between the superior angles of the scapula?, is occupied by 

 numerous small polygonal plates, analogous to those noticed in the genus 

 Actinocrinites ; these indicate that, as in those animals, an integument protected 

 by numerous plates containing in its centre the mouth, extended over the abdo- 

 minal cavity containing the viscera. This is the more strongly confirmed by a 

 fine specimen in Mr. MANTELL'S possession, and engraved for his work, PL. xvi. 

 fig. 6. which also suggests the probability that the animal was capable of con- 

 tracting this integument into the form of an imperfect proboscis. 



In two specimens which I have had an opportunity of examining, the 

 angular points of two of the costal plates where adhering to the central piece, 

 are, as well as the latter, truncated and otherwise distorted, admitting an 

 additional plate, the result of injury and restoration. But, even in this 

 instance, nature has not interrupted the general principle of muscular action, 

 continuing it over the interposed plate which is marked with ridges similar to 

 the costals. 



The remains of this species as already observed, occur only in chalk-pits, 

 and show on fracture, that they are now converted into calcareous spar, thus 

 resembling the appearance of the fracture of Pentacrinites, Asteria, and 

 Echini, found in similar strata, and thereby proving the analogy which the 

 calcareous concretions or ossicula of these animals bore originally to each 

 other. 



I entertain the hope that the parts of this animal of which I have been my- 

 self unable to speak with certainty, will be fully defined by Mr. MANTELL, who, 

 by his vicinity to the chalk-pits where it occurs, has every opportunity of 

 obtaining information and following up his inquiries. 



I cannot omit to remark that there exists a considerable analogy in the 

 arrangement of the plates forming the cup-like portion of Marsupites and 



