220 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The type series was collected by the Siboga in latitude 8 19' S. 

 and longitude 117 41' E., at a depth of 274 meters (150 fathoms). 



OPHIOTHRIX CUMULATA, new species. 



Plate 50, figs. 2-8 ; plate 51, figs. 1-5 ; plate 52, figs. 1, 2 ; plate 98, fig. 3. 



Localities. Albatross station 5112. 



Three specimens (Cat. No. E. 15, U.S.N.M.). 



Albatross station 5212; east of Masbate Island; Panalangan Point 

 bearing S. 54 30' E., 26.87 kilometers (14.5 miles) distant (lat. 12 

 04' 15" N., long. 124 04' 36" E.) ; 197 meters (108 fathoms) ; April 

 20, 1908 ;gy. S., M. 



Twenty-six specimens (Cat. Nos. 41068, E. 14, E.21, U.S.N.M.). 



Albatross station 5265. 



Twenty-seven specimens (Cat. No. E. 16, U.S.N.M.). 



Description. The diameter of the disk varies between 10 mm. and 

 13 mm. in the majority of the specimens; the arms reach 70 mm. in 

 length in an individual in which the disk has a diameter of 13 mm. 

 In the smallest the diameter reaches only 8 mm. and the length of 

 the arms varies between 40 mm. and 45 mm. 



The disk usually has a pentagonal outline, though sometimes it is 

 rounded. The dorsal surface between the large radial shields is 

 covered with small and very short club spines, which are almost 

 as long as broad and to which might well be given the name of 

 elongated granules; their outer surface carries a number of closely 

 crowded spinules, usually short and single, but capable of elongating 

 somewhat (pi. 50, figs. 6, 7 ; pi. 98, fig. 3 a) . In the smallest specimens 

 the club spines are a little more elongated, and the spinules are a 

 little stouter than in the larger ones, but these club spines scarcely 

 become elongate at the periphery of the disk, and do not pass over 

 onto the ventral surface, which is naked. The radial shields are 

 very large, triangular, almost twice as long as broad, and their length 

 equals three-quarters of the radius of the disk. The two shields of 

 each pair are in contact outwardly, and are separated throughout 

 their whole length by a narrow interval. In the small specimens 

 these shields are relatively less developed. As a ride the surface of 

 the radial shields is naked, though sometimes a few club spines may 

 be found, especially toward their proximal angle. 



The ventral surface of the disk in the interradial spaces is almost 

 entirely naked except for a very small triangular space toward the 

 periphery (pi. 51, figs. 3, 4). The genital slits are broad. 



The rather small mouth shields are lozenge-shaped, a little broader 

 than long, with two slightly excavated proximal borders; the two 

 distal sides have a somewhat variable form, and the distal angle is 

 produced into the interradial space as a more or less apparent small 



