102 BULLETIN 75, "UNITED STATES NATIONAL MUSEUM. 



OPHIOPENIA, new genus.« 



Disk covered with scales, many of which may be small and swollen 

 so as to look like coarse grains; arms short, less than twice diameter 

 of disk. Upper arm plates more or less widely separated from each 

 other. Basal under arm plates not in contact. Oral papillse few, 

 large, and ill-defined. Tentacle scales none (except on oral pore) 

 though lowest arm spine may function as one. Arm sjjines few and 

 short. Genital slits very minute, close beside first side arm plates. 



Type species. — Opliiopenia disacantha. 



This is a very curious and interesting genus, the relationship of 

 which is quite obscure. I am inclined to the opinion that it is perhaps 

 as near Opiiiozona as it is to any genus now known, but the relation- 

 ship even with that genus is certainly not close. The distribution of 

 the genus appears to be very restricted, as it has been taken only once 

 outside Bering Sea and the vicinity of the Aleutian Islands. Most of 

 the specimens were taken in quite shallow water, but a few were col- 

 lected at depths of 100 to 225 fathoms. Cold water seems to be an 

 essential feature of the habitat, as tlie temperature range is only from 

 43° down. 



OPHIOPENIA DISACANTHA, new species, b 



Disk 10 mm. in diameter; arms about 15 mm. long. Disk pentag- 

 onal, flat, covered with hundreds of small angular scales, among 

 which the centrodorsal and a marginal plate in each interradius are 

 quite distinct (in younger individuals, fig. 38a, larger radial plates 

 are easily distinguished and the radial shields may be very conspicu- 

 ous). Radial shields entirely concealed beneath the coat of small 

 scales, or if visible, widely separated and much longer than wide. 

 Upper arm plates transversely oval, much wider than long, those on 

 basal half of arm separated from each other and completely sur- 

 rounded by numerous minute scales like those of disk; these scales 

 extend far down on each side between side arm plates. Interbrachial 

 spaces below densely covered by minute angular plates, which may 

 even extend a little ways onto under surface of arm. Genital slits 

 very minute, crescent-shaped, lying, one on each side, against inner 

 corner of first side arm plate; genital scales completely hidden. Oral 

 shields small, transversely oval. Adoral plates very large, oblong but 

 nearly as wide as long. Oral plates ill-defined swollen into a sort of 

 knob at proximal end, which looks like an oral papilla. Oral papillae 

 ill-defined, apparently two on a side, outer flatter, inner more round 

 and swollen; at apex of jaw there are from one to several indistinct 



o^O^^f , signifying snake, and nsvm, signifying poverty, in reference to the lack of 

 tentacle scales and the small number of oral papillae, and in keeping with the custom- 

 ary formation of ophiuroid genera. 



bJcc, signifying twice, double, and aKavOa, signifying spine, in reference to the pres- 

 ence of only two arm spines. 



