EASTERN TROPICAL PACIFIC ASTEROIDEA. 79 



separated by only an insignificant bare deviation on the upper edge of the supero- 

 marginal plate, and by a similar low knob about twice as large on the lower 

 edge of the inferomarginals; distally these knobs become gradually longer and 

 more conspicuous, though not noticeably higher, and finally, between the sixth 

 and seventh organs on each side, they permit the merging of the organs only 

 along the Une between the upper and lower marginal plates. In large specimens, 

 the low elevations on the inferomarginals bear scattered, small spinelets of 

 diverse sizes. 



In another particular, magnus differs markedly from the other two species 

 of the genus, and that is in the series of abactinal plates which extends to the 

 tip of the arm or nearly so. In a specimen with R = 23 mm. this series is .60 

 mm. wide clear to the terminal plate; the plates composing it are of irregular 

 size and form and show no definite arrangement; they are largest distally (but 

 not close to the terminal plate where they are very small) and some of them may 

 be fully .60 mm. across; the larger plates and even the smaller distal ones bear 

 no spinelets but have a smooth, slightly convex surface. In a large specimen, 

 with R = 73 mm., the plates do not reach the extreme tip of the arm, but are 

 shut off from the terminal plate by the meeting of three pairs of superomarginals ; 

 the plates are more angular and flatter than in the smaller specimen and their 

 surface is somewhat coarsely shagreened; there is a very abrupt transition 

 from the small spinelet-bearing plates of the disk to the bare median series of 

 the arm; this occurs about 35 mm. from the arm-tip. 



The disk and cribriform organs are yellow-biown in the preserved speci- 

 mens, with all the marginal plates, bare plates of arms and whole lower surface 

 more or less nearly white. In size the range is from R = 23 to R = 98 nrni. 



Station 4647. Eastern Tropical Pacific, 4° 33' S., 87° 42' 30" W., 2,005 fms. Bott. temp. 35.5°. Lt. 



gy. and br. glob. oz. 

 Station 4649. Eastern Tropical Pacific, 5° 17' S., 85° 19' 30" W., 2,235 fms. Bott. temp. 35.4°. Fne. 



stky. gy. m. 

 Station 4658. Eastern Tropical Pacific, 8° 30' S., 85° 36' W., 2,370 fms. Bott. temp. 35.3°. Fne. gn. 



m., mang. nod. 

 Station 4717. Eastern Tropical Pacific, .5° 11' S., 98° 56' W., 2,153 fms. Bott. temp. 35.2°. Rd. c, 



glob. oz. 



Nine specimens. 



Styracaster monacanthus. 

 Plate 2, fig. 1, 2. 

 Ltjdwig, 1907. Zool. Anz., 31, p. 315. 



While the original description of this unique specimen is adequate, LudAvig 

 does not discuss its relationship to other members of the genus, although he 



