86 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



15 mm., we shall find the following differences: The radial shields which are dis- 

 tinct, though small, in O.fraterna, are altogether indistinct in 0. aculeata where 

 they are covered over with stumps identical with those existing on the rest of 

 the upper face of the disk, and radial ribs never appear in the latter. The mouth 

 shields have about the same shape in both species, but the adoral plates do not 

 separate the mouth shield from the first lateral brachial plate in 0. fraterna, while 

 they do separate it in 0. aculeata. The upper brachial plates are smaller, con- 

 tiguous from the base of the arms in the largest samples of the first species, while 

 they are larger, widened, and separated from the base in the second one. The 

 upper brachial plates always remain very wide and wider than long in 0. fraterna, 

 while in 0. aculeata their width rapidly decreases and they become as long as wide, 

 and then longer than wide. The brachial spines are a little rougher in 0. fraterna 

 and the tentacular scale is a little more widened than in 0. aculeata. 



I shall discuss a little further the affinities of 0. fraterna with 0. pentacrinus, 

 after having described the latter species. 



OPHIACANTHA GRANULIFERA Verrill. 



Plate 10, figs. 2-3. 



Ophuuxmtha granulifera VERRILL (86), p. 546. 

 Ophiacantha granulifera VERRILL (99a), pp. 321 and 324. 



Albatross station 2069. Sept. 1, 1883. Lat. 41 54' 50" N.; long. 65 48' 

 35" W.; Georges Bank; 101 fathoms; s. st. g. p. and c.; temp. 42 F. One 

 specimen. 



The specimen which has \teeo. lent me was determined by Verrill. As his 

 description, although sufficient to allow the species to be identified, is rather short 

 and not accompanied with any drawings, it has seemed to me useful to give a few 

 notes on the specimen in hand and to reproduce two photographs of it. 



The diameter of the disk is 10 mm.; the arms are not complete; they are 

 broken at 40 mm. from then- bases and must have reached about 50 mm. 

 The disk is rounded, excavated in the interradial spaces. The upper face is uni- 

 formly covered with, little rounded granules, which are very dense although not 

 absolutely contiguous, and have a rough surface; these granules are most regularly 

 arranged and all of them have the same diameter. They almost completely hide 

 the limits of the plates which carry them; however, the latter appear very dis- 

 tinctly, in my specimen, at the periphery of the disk and on each side of the 

 radial shields; these plates are fairly large, somewhat unequal and imbricated. 

 The radial shields are visible on their whole length; they are narrow and elongated, 

 triangular, three or four times longer than wide and completely bare; the two 

 shields of each pair are widely separated from each other by several rows of plates. 

 The under face is completely deprived of granules and covered with fairly large, 

 unequal, and imbricated plates. The genital slits are narrow and elongated. 



The rather small mouth shields are very wide and include a chief part, which 

 is triangular, short, three times wider than long, with a very obtuse proximal angle 

 and rounded lateral angles; the distal side, which is convex, offers in its middle a 

 widened and very much elongated lobe, the length of which reaches that of the 

 chief part of the plate; this lobe strongly protrudes into the interradial space, and 



