A. E. Verrill — JVbrth American Ophiuroidea. 341 



Ophiacantha scutata Lyman. 



Ophiacantha scutata Lym., Bull. Mus. Comp. Zool., vol. v, p. 329, pi. i, figs. 

 1-3, 1878 ; op. cit., vol. x, p. 261, 1883 (variations). 



Specimens sent to me by Mr. Lyman differ somewhat from his 

 figures and descriptions. 



The oral papillre may be either three or four on different jaws of 

 the same specimen ; they are rather stout, spiniform, the inner 

 largest, and all appear to be on the buccal plate, but the jaw-plates 

 and adoral shields are so closely united together that the sutures are 

 mostly invisible. There is often an extra outer papilla of small size, 

 Avhich is situated at the union of the buccal and adoral plates, out- 

 side the oral tentacle-pore, Avhich is large, but situated inside the 

 mouth-slit. Tooth-papillffi may be from two to four on different 

 jaws of a large specimen. Usually there is a stout median one with 

 a pair of smaller ones just above it, invisible from below, and 

 another small median one outside. The last is often lacking, and 

 the upper pair may be replaced by a single one, which is, perhaps, 

 absent in small specimens. The oral shield is more nearly transverse- 

 elliptical than figured, with a more obtuse inner angle. The madre- 

 poric shield is longer than the others and more rhombic, thickened, 

 with a median concavity. The adoral shields of a large specimen 

 are smaller than figured, narrow and tapered proximally, and the 

 ends do not meet medially, but in small specimens they are nearly 

 as figured and meet medially. The first under arm-plate is small, 

 rounded, emarginate on the inside, with, a small vertical crest at each 

 side, directed inward. 



The under arm-plates of the larger specimen are unlike the figure; 

 they are narrower and longer, with the distal end projecting and 

 strongly convex; the proximal end is very obtusely angulated or 

 subtruncate ; a little farther out on the arm they become more 

 oblong, with the outer end more projecting and the inner end trun- 

 cate and scarcely narrowed. They are slightly separated. 



Tentacle-scales, on two or three of the basal joints, are flat, erect, 

 lanceolate, and cuspidate ; occasionally, in the larger examples, 

 there are two on the first joint. Beyond the fifth or sixth joint they 

 become slender, acute, spiniform. The first two or three pairs of 

 tentacles are decidedly larger than those beyond. 



Arm-spines, in the largest rows, are ten, shaped about as figured, 

 with numerous small, sharp prickles on all sides. The basal rows 



