390 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



distant (lat. 9 13' 00" N., long. 118 51' 15" E.) ; 2,021 meters 

 (1,105 fathoms) ; April 3, 1909; gy. M. 



Two specimens (Cat. Nos. 40923, 40924, U.S.N.M.). 



Description. The diameter of the disk is 14 mm. ; the arms are all 

 incomplete. 



The disk is pentagonal with the borders concave and the angles 

 pass imperceptibly into the arms. The dorsal surface is covered with 

 numerous plates of medium size which are fairly uniform and 

 slightly imbricated. The dorso-central plate is a little larger than 

 those adjacent, but it is scarcely distinguishable from them, and the 

 primary radials can not be recognized. On the border of the disk 

 in each interradial space there is a larger plate which is rounded and 

 transversely broadened. The radial shields are rather large, much 

 elongated, twice or two and a half times as long as broad, triangular, 

 with the angles very rounded and separated throughout their whole 

 length by a broad space occupied by a row of plates ; the length of 

 these shields is slightly less than half the radius of the disk. 



The ventral surface of the disk in the interbrachial spaces is cov- 

 ered by rather numerous small plates fairly uniform in size and im- 

 bricated. The genital plates are very narrow and elongated. The 

 genital slits, which are also very narrow, extend as far as the border 

 of the disk, and they are furnished, on both borders, with small, low, 

 and rounded papillae. The papillae of the interradial row may be 

 continued somewhat toward the outer border of the radial shields 

 and even onto the border of the disk, and some of them may elongate 

 into small and very short spines which may even occur at some dis- 

 tance from the arms. 



The mouth shields are rather large, as long as broad, or a little 

 longer than broad. They show a triangular principal portion which 

 is longer than broad with a proximal angle and very convex sides; 

 the lateral angles are much rounded. This part is followed by a 

 quadrangular and somewhat narrower distal lobe terminated by a 

 convex border; the dividing line between these two parts is marked 

 by the bottom of the genital slit, which forms a slight notch. The 

 adoral plates are much elongated, extremely narrow in the part ad- 

 jacent to the mouth shields, which represents three-fifths of their 

 length, and strongly broadened outwardly in such a way as to sepa- 

 rate the mouth shield from the first side arm plate over a very con- 

 siderable space along which they border the genital slit ; this portion 

 which delimits the bottom of the genital slit bears a row of papillae 

 identical with those along the rest of the slit. The oral plates are 

 large and high. The lateral mouth papillae are six and sometimes 

 seven in number; the first is rather small and quadrangular, the sec- 

 ond is also quadrangular, but very much larger, and the following 



