88 THE ATLANTIC. [chap. ii. 



radial, or " radial axillary," which is united to the second radial 

 by a syzygy, the upper border of the plate is nearly straight ; 

 but it is divided into two facets for the articulation of the two 

 first brachials. The ridge is continued from the second radial 

 to about the middle of the third, where it divides, and its 

 branches pass to the insertions of the first brachials, to be con- 

 tinued along the middle line of the arms. The wing -like 

 lateral processes are continued along the sides of the radial axil- 

 laries, and along each side of, at all events, the first three bra- 

 chials. The arms are ten in number ; in the larger specimens 

 they are about 30 mm. in length, and consist of from forty to 

 fifty joints. The first and second and the fourth and fifth bra- 

 chials are united by syzygies, and after that syzygies occur 

 sparingly and at irregular intervals along the arms. There are 

 no pinnules on the proximal joints of the arms, but toward the 

 distal end there are usually about twenty, in two alternating 

 rows ; the number and amount of development of the pinnules 

 seem to depend greatly on age, and not to be very constant. 

 The arms and the pinnules are deeply grooved, and along the 

 edges of the grooves are ranges of imbricated reniform plates, 

 cribriform and very delicate, much resembling those in the 

 same position in JRhizocrinus. The disk is membranous, with 

 scattered calcareous granules. The mouth is subcentral ; there 

 are no regular oral plates, but there seems to be a determina- 

 tion of the calcareous matter to five points round the mouth, 

 where it forms little irregular calcareous bosses. There is an 

 oral ring of long fringed tentacles, and the tentacles are long 

 and well marked along the radial canals. The excretory open- 

 ing is on a small interradial papilla. The ovaries are borne 

 upon the six or eight proximal pinnules of each arm. This 

 form appears to be in some respects intermediate between the 

 pentacrinoid stage of Antedon and Rhizocrinus. I shall re- 

 serve a discussion of its systematic position until I have an 

 opportunity of describing it more in detail. 



