ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER 17 



the ridges themselves are covered with minute pedicellariae. The first complete 

 ridge usually meets the fifth adambulacral plate. 



Lateral spines very slender and fragile, usually closely appressed to side of ray. 

 On the genital region they are about 7 mm. long (four adambulacral plates in length) . 

 At the middle of ray a spine measures 8 mm. (4.6 adambulacral plates) in length. 



Adambulacral plates slender, as usual in this genus, with a very concave furrow 

 margin. Armature: On the first 3 to first 14 plates is a delicate furrow spinelet about 

 as long as half the length of plate (or less) and spaced a third the plate's length from 

 the adoral end. Over the rest of ray there is no furrow spinelet. There is one slender 

 subambulacral spine situated just aborad of the middle of the plate. It is 4 mm. long 

 (two adambulacral plates), or on alternate plates, between lateral spines, a little 

 longer. The subambulacral and lateral spinelets normally are covered with a delicate 

 sacculus beset with minute pedicellarise. 



The first and second adambulacral plates are joined by syzygy, or nonmuscular 

 articulation. The first adambulacral plates of adjacent rays are separated, as in 

 exilis, by the outer ends of the combined mouth plates. Interradial angle formed by 

 the first marginal of each ray, which lies along the upper edge of the first adambulacral 

 plate. These marginals join by their inner end and are also joined to the lower end 

 of the interradial plate. The articulation surface of the ambulacral ossicle (the distal 

 face of the second) where ray has been removed, is very small, broadly elliptical, and 

 the combined width of the pair is considerably more than the height. They are 

 smaller and broader than in exilis. The second ambulacral ossicle is two-thirds to 

 three-fourths the length of the first, measured on summit of ridge. 



Mouth plates small, very similar in form to those of exilis but slightly narrower. 

 Armature: One or two actinostomial spinelets; when there are two, one is usually 

 directed over the peristome and one across mouth of furrow; rarely there may be an 

 aboral furrow spinelet. There is one slender, sharp, suboral spine situated on the 

 middle of the plate, and equal to the length of the first two adambulacral plates. In 

 some specimens the marginal spinelets are absent. 



Type.— Cat. No. E. 1414, U.S.N.M. 



Type-locality. — Station 4427, off Point San Pedro, Santa Cruz Island, Calif.; 

 447 to 510 fathoms, black mud and rocks; 18 disks, 15 rays, more or less broken. 



Distribution.— OS southern California, from San Diego to Santa Cruz Island, 

 301 to 1,059 fathoms, green and black mud. 



Specimens examined. — Five disks, 27 rays, from the following stations: 



Station 4333, off Point Loma, Calif. (13.6 miles southwest), 301-487 fathoms, 

 green mud; bottom temperature, 40.1° F.; about 16 rays, in fragments, one disk. 



Station 4387 (probably 4387a), vicinity of San Diego, Calif., 32° 32' 40" N., 

 118° 04' 20" W.; 1,059 fathoms, green mud; three disks, nine broken rays. 



Station 4416, off Santa Barbara Island, Calif., 448 fathoms, dark green mud; 

 disk and two rays, broken. 



Remarks. — The differences which separate this species from exilis are mentioned 

 in the synopsis, the diagnosis, and the foregoing description. It differs from B. tene.Ua 

 (Ludwig) in having widely spaced costae which extend three-fourths the length of 

 ray, in having no furrow spinelets except a small adoral one on the first few plates of 

 the series, and in having much smaller articulation facets on the proximal face of 



