56 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



only as far as the fifth inferomarginal, but a single series of small 

 plates (which are rudimentary distally) reaches the fourteenth in- 

 feromarginal. 



Furrow margin of the adambulacral plates is angular as in 

 analog us (but in the midregion of the ray not so strongly so), and 

 there are 12 to 14 furrow spinelets, webbed for nearly half their, 

 length, the median spinelets being slightly the longest. Four or 5 

 shorter spinelets stand on the outer border of plate, immersed in 

 membrane, one of them becoming a specialized subambulacral spine 

 on the midregion of ray (but not enlarged on the- distal or proximal 

 part of the ray) . 



The transverse margins also bear 1 to 4 immersed spinelets. With 

 the excei^tion of the first and second, or first and third plates, the 

 outer edge of the proximal adambulacrals not separated by a furrow 

 from the actinal intermediate plates as in analogus^ but the mem- 

 brane is continuous. The first plate is scarcely compressed. 



Mouth plates very prominent actinally. The marginal series of 

 12 spinelets is angular, giving the inner end of the combined pair 

 a truncate apj)earancef but the series does not dip down into furrow 

 •quite so conspicuously as in analogus^ although somewhat. The in- 

 ner spine is enlarged into a conical tooth and just above it one or two 

 suboral spines are similarly enlarged. Numerous smaller spines are 

 scattered over the surface of plates. 



Madreporic body situated its own diameter from marginal p'lates, 

 its width equaling the length of three interbrachial superomarginals 

 (one and a half in analogus). Striae fine, radiating from an eccen- 

 tric point (nearer the adcentral margin than outer edge). In 

 analogus they radiate from an interradial point on the adcentral 

 margin. 



Type.— Cdit. No. 30508, U.S.N.M. 



Type-locality.— Station 5425, Sulu Sea (lat. 9° 37' 45" N.; long. 

 121° 11' E.), 495 fathoms, gray mud, coral sand, bottom temperature 

 49.40° F. 



Distrihution. — Sulu Sea and off Southern Luzon, Philippine 

 Islands, 338 to 495 fathoms. 



Specimens examined. — In addition to type, 1 from station 5373, 

 off Marinduque Island (south of Luzon), 338 fathoms, soft mud, 

 bottom temperature 51.8° F. 



PRIONASTER MEGALOPLAX Fisher. 



Plate 4, fig. 3 ; plate 5, fig. 1 ; plate 9, fig. 2, 2a-h. 



Prionastcr mcr/aloplax Fisher 1913a, p. 603. 



Diagnosis. — Differing from Prionaster aTialogus in the following 

 features : Large compact paxillae with very numerous spinelets ; large 

 madreporic body; superomarginals not in contact distally; supero- 



