438 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



strongly notched at the base of the arms, and it includes at least the 

 two first upper arm plates. This surface is covered with fine and 

 closely crowded granules, which occur over its whole extent and en- 

 tirely cover the radial shields ; thanks to a slight difference in color, 

 the outlines of these shields may however sometimes be distinguished, 

 and they are seen to be elongated and oval, those of each pair widely 

 separated from each other, and also separated from the first upper 

 arm plate, by several rows of granules. The distal extremities of 

 the genital slits which pass on to the dorsal surface in accord- 

 ance with the characteristics of the genus, extend almost to 

 the level of the proximal border of these shields, and they are sepa- 

 rated from the first upper arm plates by several rows of granules. 

 This dorsal part of the genital slits is bordered by granules some- 

 what more elongated than those adjoining; it is very narrow and 

 sometimes only slightly evident, though it can always be recognized, 

 .and there is not doubt regarding the generic position of the ophiuran. 



The ventral surface of the disk is naked over the greater portion of 

 its surface and it show r s at the periphery a narrow border of gran- 

 ules which continues along the genital slits; this peripheral border, 

 which includes at first three or four rows of granules, becomes 

 reduced to a single row on the proximal third of these slits. It is 

 probable that this denudation of the ventral surface of the disk is 

 accidental, but I can not state this in a definite manner. The por- 

 tions of the ventral surface which are without granules are covered 

 with small unequal plates, which are irregularly polygonal and not 

 imbricated. The genital slits are of medium size and slightly broad- 

 ened at their proximal extremity in such a way as slightly to notch 

 the sides of the corresponding mouth shields. 



These shields are rather large, a little longer than broad, and 

 pentagonal, with a rather open proximal angle bordered by two 

 straight sides passing over by very rounded angles to the two lateral 

 sides which are slightly convex and notched toward their proximal 

 third by the bottom of the genital slits. These sides also pass over 

 by rounded angles to the distal border, which is itself slightly 

 rounded. The adoral plates are much elongated and very narrow, 

 in contact in the median interradial line ; they broaden a little out- 

 wardly and form a small lobe separating the mouth shield from the 

 first side arm plate. The oral plates are triangular, twice as high as 

 broad, and covered in the neighborhood of the median interradial 

 line by a group of rounded granules a little larger than those of the 

 disk. The two or three granules which cover the tip of the oral 

 plates are slightly elongated in the direction of the mouth. The 

 mouth papillae usually number six on either side. The outermost 

 papilla is large, squamiform, very much broadened, at least three 

 times as long as broad, a little broader inwardly than outwardly, with 



