26 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



Lateral spines opposite alternate adambulacral plates. They are very slender 

 but are heavily sheathed with membrane. At the middle of the genital area they 

 are about the length of four adambulacral plates, and beyond the genital region, of 

 5 to 5.5 adambulacral plates. The pedicellariae covering the sheaths are very small. 



Adambulacral plates of genital region short, the width at first exceeding the 

 length, but at the outer limit of the genital region the plates are slightly longer than 

 wide. Armature consists of one aboral furrow spinelet, a little shorter than the plate 

 (measured at middle of actinal face) and one subambulacral spine next to the aboral 

 border, but on the first 10 plates occupying a considerable part of the surface of plate. 

 The furrow spinelet is sometimes clavate at the tip, and its sheath is rather plentifully 

 supplied with small pedicellariae. A variable number of the proximal subambulacral 

 spines usually from about the third to the tenth or twelfth, have a truncate swollen 

 tip, which varies considerably in size. Sometimes it is scarcely broader than the 

 rather thick spine; again, it is nearly twice the breadth near tip. These proximal 

 spines are a trifle over two adambulacral plates in length; farther along, after they 

 become sharp, they are about three plates long. The pedicellariae are on the outer 

 side of the spine. On the terminal portion of the ray the furrow spinelet is lacking. 



The first adambulacral plate is not in contact with that of the adjacent ray, 

 the outer end of the combined mouth plates leaving a narrow interval between the 

 two. There is no syzygy between the first and second adambulacral plates. 



The articulating surface of the ambulacral ossicles, after a ray is detached, is 

 small, broad above and narrow below, rather narrowly cordate in outline. 



The mouth plates are rather broad at the outer end. Actinostomial margin 

 with three spinelets, the innermost the shortest, and occasionally there is a rudi- 

 mentary spinelet on the furrow margin adjacent to first adambulacral plate. Each 

 plate bears one suboral spine about as long as the first two adambulacral plates. 



Anatomical notes. — Gonads, two to each ray with six or seven divisions to each, 

 which extend along the ray a distance only a little greater than the diameter of disk. 

 The coeca extend about twice as far; or to the end of the genital region. The inner 

 surface of the ambulacral ossicles is smooth. Although the proximal adambulacral 

 plates of adjacent series are not in contact at the base of ray, they are not separated 

 by an azygous plate as in Colpaster. The narrow exposed outer part of the combined 

 mouth plates intervenes between the proximal ends of the first adambulacral plates 

 of the two adjacent series, and continues upward to abut against the lower end of 

 the interradial plate. The surface of this dorsal extension of the oral plates is flush 

 with that of the interradial plate. The dividing suture between the two dorsal parts 

 of the pair is at the bottom of a shallow sulcus which is continued above upon the 

 surface of the interradial plate. Unless the specimen is dry or treated with caustic 

 potash, it is not easy to distinguish the dividing sutures, and consequently the three 

 plates appear to be one large interradial plate. The outer sides of each of these 

 dorsal extensions abuts against the first adambulacral below and the second adam- 

 bulacral above. The upper end as mentioned above rests against the lower end of 

 the elongate, narrow, vertical interradial plate. (PI. 4, fig. la.) 

 Type.— Cat. No. E. 1415, U.S.N.M. 



Type-locality.— Station 3342, off British Columbia (52° 39' 30" N., 132° 38' W.); 

 1,588 fathoms, gray ooze and coarse sand; bottom temperature, 35.3° F.; 12 speci- 



