620 PROCEEDINGS OF THE XATIOXAL MUSEUM. vol.43. 



PERSEPHONASTER MONOST<ECHUS, new species. 



Related to P. croceus Alcock and Wood-Mason, which it resembles 

 in having, in addition to the appressed inferomarginal spines, a conical 

 erect lateral spine, but differs in having only 1 series of erect supero- 

 marginal spines (peculiarly situated), narrower marginals, 8 furrow 

 spines, small actinal interradial areas, and irregularly occurring and 

 smaller, erect, lateral spines. R=45 mm., r = 8.5 mm., R=5.3 r; 

 breadth of ra}^ at base, 12 mm. Rays rather slender, with proximally 

 high, lateral walls sloping steeply but not quite perpendicularly; 

 marginal plates massive, tumid, the superomarginals encroaching 

 conspicuously ui:>on the abactinal surface beyond the base of ray. 

 Interbrachial angle abruptly rounded. 



Type.— Cat No. 30528, if.S.ISr.M. 



Type-locality . — Station 5606, Gulf of Tijniini, Celebes, 834 fathoms, 

 green mud. 



The paxillas are comparatively large, though having on an average 

 15 to 18 pointed, slender spinclets about as long as the convex tabu- 

 lum, 3 to 5 occupying the center. Paxillss are largest in the inter- 

 radial regions and adjacent portions of ray, base of tabulum roundish 

 on disk but on ray the plate as well as section of tabulum is elongate- 

 elliptical. On radial region of each ray are several large fasciculate 

 pedicellariae sometimes broader than paxillse, composed of 4 to 8 

 pointed tapering spinelets, much stouter than those of paxillse, and 

 springing from low plates resembling reduced paxillse. First 4 or 5 

 superomarginals with the single upright conical spine ])ractically on 

 upper edge of plate, but with the fifth plate the spine recedes from 

 the inner edge and more and more of the surface of the plate is 

 abactinal. With the eighth or ninth plate the 2 facets are about 

 equal, but distally from this point the dorsal becomes much the 

 wider and the spine wliich keeps on the well rounded margin between 

 the 2 facets gradually becomes horizontal and has the aj)pearance of 

 being a lateral spine. There is no abrupt fasciolar channel between 

 the plates, the surface sloping upward from either transverse suture 

 to the median Ime, and the spine is on this ridge. All except the 

 distal inferomarginals are tumid, the ridge of the superomarginals 

 being continued across the lower series, and the ventral margin of 

 the ray is so evenly rounded that the plate is regularly curved from 

 the inner to outer edge. The armature is quite distinct from that 

 of the foregoing species. Just below the outer or upper edge of the 

 plate is a horizontal, erect, conical spine, a little smaller than the 

 corresponding superomarginal. Below this and forming with it a 

 slightly oblique transverse comb are 2 (sometimes 3, and distally 

 only 1) slender, appressed, slightly flattened, sharp spines, the u])per 

 about as long as the width of plate. The erect conical spine is often 

 missing. The furrow spines are 8, long, slender, slightly com- 



