i6o DISCOVERY REPORTS 



Genus Rhopiella^ nov. 



Diagnosis. Small Antarctic Echinasteridae superficially resembling Poraniopsis, but 

 diff"ering in having a small spine on the furrow face of the adambulacral plates, in lacking 

 intermarginal papulae, and in having gonopores in the actinal interradial area. Diflfering 

 from Echinaster, sensu stricto, in the extensive actinal intermediate areas and in the 

 adambulacral armature, which consists of a transverse comb of spines united by delicate 

 membrane essentially as in Pteraster. Paedophoric. Type, Rhopiella koehleri. 



Remarks. This group includes also Echinaster hirsiiius Koehler,^ E. pterasteroides 

 Koehler,^ and possibly E. smilox Koehler.* These species have a general facies unlike 

 that of the tropical and warm water species constituting the genera Echinaster and 

 Othilia, a fact which evidently troubled Koehler (1920, p. 118). 



In keeping with the larger disk, the interbrachial septum is rather strongly fortified 

 with calcareous plates. The septal fold extends from the body wall inward to a concave 

 free edge impinging on the stomach, the dorsal " attachment " reaching three-fourths the 

 distance from margin to centre of disk {R. koehleri). 



The skeleton of Koehler's Echinaster smilax is close-knit in contrast to the other 

 species in which it is very open, while the spinelets are more simple. The terminal 

 portion is not expanded, denticulate, and hyaline as in R. koehleri, hirsuta and pteraster- 

 oides. Yet in the large disk, proximally swollen rays, and structure of the adambulacral 

 armature smilax seems to be nearer to Rhopiella than to Echinaster. 



Rhopiella koehleri sp.nov. 

 (Fig. E, 2-2 d; Plate X, figs, i, 2) 



Diagnosis. Resembling Rhopiella hirsuta (Koehler),'^ but with only a few large 

 papulae scattered over the abactinal area; not more than a single papula to a skeletal 

 mesh and numerous meshes without a papula. Whole body covered by a soft opaque 

 skin, forming a thick sheath on spinelets, and a delicate web uniting the transverse comb 

 of usually 5 adambulacral spinelets, R 33 mm., r 10 mm., R = 3-3r; br lo-ii mm. 



Description. The general habit and the structure of the skeleton is like that of 

 hirsuta. Koehler states that the number of papulae varies, in hirsuta from i to 5 or 6, 

 according to the dimensions of the skeletal interval. In koehleri there is never more than 

 one large papula to an interval and there are numerous meshes without a papula. There 

 are no intermarginal and no actinal papillae. 



The primary plates, which are irregularly lobed, carry i or 2 spinelets, i-i-2 mm. long ; 



^ Derived from Rhopia, Gray, a synonym of Echinaster, seiisu stricto. 



2 Koehler, 1920, p. 113, pi. 12, fig. 9; pi. 24, figs. 6-9; pi. 66, fig. 2. Type locality, 66° 32' S, 141° 39' E, 

 151 fathoms. 



3 Koehler, 1920, p. 115, pi. 16, figs. 4, 5, 8; pi. 25, figs. 3, 4, 5; pi. 66, fig. 3. Type locality, 64° 44' S, 

 97° 28' E, 358 fathoms. 



* Koehler, 1920, p. iii, pi. 12, fig. 10; pi. 25, figs, i, 2, 6, 7; pi. 66, fig. i. Type locality, 66° 8' S, 94° 17' E, 

 120 fathoms. 



* Koehler, 1920, p. 113, pi. 12, fig. 9; pi. 24, figs. 6-9; pi. 66, fig. 2 (as Echinaster hirsutus). 



