1885.] NATUKAL SCIENCES OF PHILADELPHIA. 353 



pieces, but they undergo more variations among species, and show- 

 more irregularities than any of the other plates. In some species 

 they are confined almost exclusively to the upper face, being mere 

 top pieces ; in others they represent an important part in the par- 

 tition walls, while in still others they extend deeply down into 

 the tubular neck, forming the upper part of its walls. In all 

 cases, however, their obtuse edges are turned outward, and form 

 the upper part of the partition, being suturally connected with 

 the lower part of them. 



The plates covering the tubular neck, i. e., anal plates, consist 

 of small pieces, with a somewhat subcentral opening, or, as in 

 Eucalyptocrinus rigens Angelin, of valvular plates. Sometimes 

 they are extended into a free tube, composed of hexagonal pieces. 

 The arrangement of the plates surrounding the anal opening is 

 more regular than it appears from some specimens. The apparent 

 irregularities are caused largeby by the plates of the third ring, 

 which, in some species, have their upper ends partly exposed. 



The arms are arranged in pairs, each pair filling one of the ten 

 compartments, with an interradial partition wall on one side, and 

 an interaxillary one on the other. The arms evidently moved 

 with difficulty, being heavy, and in the adult composed of two 

 rows of short transverse pieces, with horizontal sutures, but there 

 was a single row of wedge-shaped pieces in 3 r oung specimens. 

 They have a deep ventral furrow, and long pinnules composed of 

 numerous joints, which gradually decrease in width. The arms 

 and pinnules are so closely fitted into the partition walls, that 

 when the arms are perfectly closed, it appears as if they were 

 suturally connected and constituted a part of the body. 



The visceral cavity actually is formed only by the plates of the 

 dorsal cup and by the two lower rings of plates in the vault, the 

 plates of the two upper ones forming the neck-like prolongation. 

 The food grooves enter the calyx at the base of the arms, and 

 proceed within shallow grooves at the inner floor to near the top 

 of the second ring. The hydrospires evidently extended to the 

 lower portion of the neck, and perhaps (?) communicated with 

 the exterior through the anal aperture, as apparently no other 

 opening except the ambulacral passages enter the body. 



The column is moderately large, cylindrical, composed of rather 

 long joints, with pentapetalous central canal. It evidently had no 

 lateral cirrhi, except at the root, where it gives off hundreds of 



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