OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 125 



The upper face of the arms is covered with a set of large lamellae, each of which 

 undoubtedly represents an upper brachial plate. These lamellte are very large, 

 quadrangular, wider than long, and widened on their distal side, which is slightly 

 rounded; the lateral sides are slightly divergent. Tlieir surface displays extremely 

 fine lines bounding hexagonal fields which are very dense and minute. These 

 lamellae are exceedingly thin and completely transparent, so that they allow the 

 imdcrlying parts to be seen, the color of which is white above the vertebra and 

 brownish above the muscles. 



The first brachial under plate is large, oval, and transversely widened. The 

 following ones are quadrangular, longer than wide, their proximal edge being 

 straight and narrower than the distal side which is broad and convex; this side most 

 generally shows three distinct littl-e lobcsj the lateral sides are divergent and rather 

 strongly excavated by the con-esponding tentacular pores, which are very large. 

 From the sixth plate upward the proximal side is replaced by an acute and elon- 

 gated angle; the plates are then no longer contiguous, and, at the same time, they 

 become much narrower in their middle region, owing to the extension of the ten- 

 tacular pores, their distal side remaining still very wide and trilobed. 



The tentacular pores are very large, rounded, and deprived of scales, excepting 

 the oral pores which are each provided, on their interradial edge, with three conical 

 and elongated papillae wliich are inserted near the end of the adoral plate; the 

 external papilla is even remarkable by its elongation and it constitutes an actual 

 spine. 



The lateral plates, sUghtly protruding, carry each three subequal spines, the 

 length of which equals that of the article; these spines have rounded ends and their 

 surface microscopically appears covered with very fine, conical, and dense rugosities. 



Connections and differences. — The Ophiuran which I have just described seems 

 to me to fit perfectly in the genus OpJtioleptoplax recently introduced by H. L. 

 Clark (11, p. 278). The type of this genus is 0. megapora, which was discovered by 

 the Albatross in the Japanese seas at lat. 32° 26' N. and long. 129° 27' 30" E. at 

 a depth of 71 fathoms. The new species differs from it in ha\'ing larger mouth 

 shields, much more elongated adoral plates, more developed mouth and tooth 

 papiUae, in having papiUae on the tentacular oral pores, and, lastly, in having much 

 more elongated under brachial plates. 



OPmOBYRSELLA OUADRISPINOSA, new species. 

 Plate 16, figs. 2-3. 



Albatross station 2343. Jan. 19, 1885. Lat. 23° 11' 35" N.; long. 82° 19' W.; 

 279 fathoms; fne. co. Two specimens. 



Type.— C&t. No. 32305, U.S.N.M. 



The diameters of the disks are respectively 19 and 22 mm.; the arms are 

 exceedingly long, very sinuous, and their length exceeds 170 mm. in the larger 

 specimen. 



The disk is pentagonal with rounded angles. The upper face is covered with 

 a bare tegument which is deprived of plates and spines and shows only a few dense 

 and irregular folds. However, in the vicinity of the radial shields and at the margin 



