110 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



OPHIOMITRELLA EXILIS, new species. 



Plate 22, figs. 9, 10. 



Locality. Albatross station 5637: Bouro Island (S.) and vicinity; 

 Amblau Island (N.) bearing N. 80 E., 38.92 kilometers (21 miles) 

 distant (lat. 3 53' 20" S., long. 126 48' 00" E.) ; 1,280 meters 

 (TOO fathoms) ; December 10, 1909; gy. M. 



One specimen (Cat. No. 40949, U.S.N.M.). 



Description. The diameter of the disk does not exceed 5 mm., and 

 the arms are about 15 mm. long ; three of them are incomplete ; they 

 are very narrow, moniliform, and somewhat contorted. 



The disk is rounded, but rather strongly excavated in the inter- 

 radial spaces. The dorsal surface is covered with very numerous 

 plates, which are small, closely crowded, imbricated and subequal, 

 smallest in the central region and becoming a little larger toward the 

 periphery. These plates carry very small, short cylindrical club- 

 spines, which are as long as broad, each terminated by a crown of 

 half a dozen fine and elongated spinules. These club spines are lack- 

 ing on a rather large portion of the surface of the disk, but they have 

 certainly been rubbed off. The radial shields are small, triangular, 

 with a proximal apex; they are twice as long as broad, and their 

 length does not even reach a quarter of the radius of the disk ; the two 

 shields of each pair are widely separated by a space which is almost 

 equal to the width of the arm. 



The ventral surface of the disk in the interradial spaces is covered 

 with small, imbricated and equal plates, provided with club-spines 

 identical with those of the dorsal surface, but on which the terminal 

 spinules are shorter; these club-spines are continued to the vicinity 

 of the mouth shields. The genital slits are narrow, but very distinct. 



The mouth shields are rather large, triangular, with a sharp and 

 somewhat produced proximal angle, bounded by two slightly concave 

 sides which pass over rounded angles and unite to form the convex 

 distal border ; they are a little broader than long. The adoral plates 

 are rather narrow, elongated, at least four times as long as broad, and 

 they give off outwardly a narrow process which separates the mouth 

 shield from the first side arm plate ; their internal border is strongly 

 notched by the large external mouth papilla. The oral plates are 

 triangular, and higher than broad. The mouth papillae are four in 

 number on each side. The external papilla, borne by the adoral plate, 

 is very broad at the base, but pointed and conical ; the second is also 

 rather large and of a form similar to the preceding, but smaller ; the 

 two others are narrow and pointed. The unpaired terminal papilla 

 is stouter than the others ; it is similarly conical and pointed. 



The upper arm plates are small, triangular, and very convex ; they 

 show a rather open proximal angle and a convex distal border. They 



