EXPLANATION OF PLATE 47. 81 



Fig. 6. Body of Apiocrinites 30-dactylus (Nave Encrinite 

 of Parkinson) copied from Miller's Crinoidea, P. 98. 

 PI. 11. (See V. I. p. 323. Note.) 



Q. Pectoral Plates. 



R. Capital Plates. 



X. Orifice of the Mouth, or Proboscis, capable of elonga- 

 tion for sucking in food. 



Fig. 7. Another Body of a Nave Encrinite, drawn by Mr. 

 J. Sowerby from a specimen in the British Museum. 

 The same is Figured by Parkinson, in his Organic 

 Remains, Vol. II. PI. XVII. Fig. 3. The lateral pro- 

 jections are the commencement of the side arms. 

 This specimen has been corroded with acid, and 

 consequently has lost the superficial Corrugations and 



in his admirable Monograph on Crinoidea, p. 97. " The mechanism 

 of the joints of the side arms, where these insert into the column, is 

 well worthy of notice, particularly in old specimens. In the earlier 

 stage of their formation, the side arms being very short, and having 

 then little weight, a less firm mode of adhesion to the column than 

 becomes requisite at a subsequent period, being then sufficient, we 

 do not find more than one joint lodged in a socket, or concave impres- 

 sion on the column; but when increase of size renders a stronger sup- 

 port necessary, two or three succeeding joints of the side arms become 

 imbedded in this socket, (for which its extension as already noticed 

 allows room) and these joints instead of being arranged in a series branch- 

 ing off" at right angles from the column, become oblique, their direction 

 inclining upwards, so as to aid in bearing the additional weight. The 

 first joint of the side arms, where thus obliquely inserted in the 

 columnar socket, have that portion of their circumference which is 

 presented towards the upper part of the column, truncated, in such a 

 curve as may fit them to the concavity of the impression where they 

 rest against it. 



The surface of these joints, which fit into the columnar impression, 

 is smooth, being destined for adhesion only, but the articulating sur- 

 face between the contiguous joints, where motion also is to be allowed, 

 exhibits the usual mechanism of radiated ridges and furrows. These 

 joints are convex on the side nearest the column, and concave on that 

 most remote. 



