TWO NEW OPHIURANS CLARK 417 



Holotype.— Station 19 ; Puerto Rico ; off Puntilla Point, parallel to 

 Tablazo Shoal; 31/2 fathoms; broken shell, broken coral, and mud; 

 W. L. Schmitt, March 29, 1937 (U.S.N.M. no. E. 5590). 



Remarks. — This little Ophiactis is quite different from any known 

 West Indian species. The disk covering may owe its peculiarities to 

 being regenerated, though the appearance of the basal upper arm 

 plates does not support such a hypothesis. But the oral papillae are 

 very distinctive, and the color, the arm plates, and the arm spines, 

 taken in connection with the number of arms, give this Ophiactis a 

 status quite apart from any other species now known. 



Genus OPHIOTHRIX MuUer and Troschel 



OPHIOTHRIX PLATYACTIS, new species 



Plate 52, Figures 3, 4 



Description. — Disk 6 mm in diameter, quite flat, covered by rela- 

 tively' few scales and the 5 pairs of radial shields ; the latter are large, 

 triangular, 2 mm long and 1 mm wide distally, sharply pointed at 

 inner end; in each pair the shields are markedly separated from each 

 other, except at the distal inner corner where they may touch; the 

 surface of each shield is bare and smooth except for the presence of 

 2 to 5 minute irregularly scattered rounded granules. Disk scales 

 comparatively few, coarse and thick, not well defined; each scale 

 carries 1 to 5 rounded granules much larger than those on the radial 

 shields; at the interbrachial margins these granules are higher than 

 thick and might be called low spinelets. Interbrachial areas below 

 covered with thin overlapping scales, much more delicate than those 

 of the upper surface; near the margin of each area are a very few 

 low blunt spinelets. 



Arms 5, short and flat, probably less than 30 mm in length, wide 

 at base but slender at tip. Upper arm plates much wider than long, 

 more or less triangular with all angles rounded; the basal plates have 

 the proximal angle truncated, as they are obviously in contact with 

 each other, but this proximal margin is not half so long as the distal, 

 wliich is twice the plate length or even more and straight or flat- 

 teued-convex; the surface of the plates is very finely roughened, not 

 nearly so coarse, however, as to be called shagreenlike. 



Oral shields much voider than long, with a small blunt proximal 

 angle, a nearly straight distal margin, and rounded lateral ends. 

 Adoral plates short and wide, in contact interradially and closely 

 appressed to the proximal margin of the oral shield. No oral papil- 

 lae, of coui-se ; the cluster of tooth papillae conspicuous as usual, but 

 not peculiar. Under arm plates quadrilateral, the length and breadth 

 about equal or, near base of arms, the breadth a little greater ; distal 

 margin notably concave; proximal a trifle convex or with a low 



