184 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Albatross station 5375; Marinduque Island and vicinity; Tayabas 

 Light (outer) bearing N. 49 W., 33.73 kilometers (18.2 miles) dis- 

 tant (lat. 13 42' 15" N., long. 121 50' 15" E.) ; 196 meters (107 

 fathoms) ; March 2, 1909 ; gn. M. 



Four specimens (Cat. No. E. 4, U.S.N.M.). 



Description. I shall describe this species from one of the speci- 

 mens, from station 5375 (pi. 61, figs. 5, 6, 7), which is the largest. 

 The diameter of the disk, which is slightly deformed, is 12.5 mm. by 

 11 mm. In the other specimens the diameter of the disk is between 

 6 mm. and 8 mm. The arms are extremely long, rolled up, rather- 

 slender, and flattened ; in the specimen which I am describing their 

 length is more than 150 mm. 



The dorsal surface of the disk is covered with slender, conical, and 

 pointed spines, which are rather elongated and very closely crowded, 

 and which conceal the contours of the underlying plates ; these spines 

 become less crowded and may even be completely lacking on the cen- 

 tral region of the disk in young specimens. In the adults the con- 

 tours of the plates are always more or less obscured by the integu- 

 ment ; sometimes, however, they may be distinguished, and it is then 

 seen that they are very small in the central region of the disk, be- 

 coming a little larger toward the periphery, where they imbricate. 

 In the small specimens, like the second from station 5375 which is 

 shown in figure 9, the plates are very much more evident and larger, 

 and there is in particular a row of large plates in the middle of each 

 interradial space ; on either side of this row, the plates become smaller 

 and imbricated, while the central region of the disk is occupied by 

 small rounded plates. The radial shields are very narrow, elongated, 

 in contact throughout their whole length, and in the large specimens 

 four times as long as broad, while in the small ones they are relatively 

 shorter and somewhat broadened. 



The ventral surface of the disk is uniformly covered with small, 

 imbricated, equal plates, becoming a little larger in the vicinity of 

 the genital slits ; these plates carry spines identical with those on the 

 dorsal surface and rather closely crowded. The genital slits are 

 very narrow and elongated. 



The mouth shields are longer than broad, lanceolate, consisting of 

 a triangular major portion which is almost as long as broad with a 

 rather sharp proximal angle, of which the apex is ordinarily slightly 

 rounded, plus a lobe which projects in a variable manner into the 

 interradial space. In the large specimens (fig. 7) this lobe is less 

 developed than in the small ones in which it is narrower but more 

 elongated, as may be seen in figure 8. The adoral plates are narrow ; 

 they are especially developed on the side of the mouth shield, and, 

 behind it, they send off a process separating the mouth shield from 

 the first side arm plate; they taper in their proximal portion, and 



