232 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



. Cat. No. 25722, U.S.N.M., from station 4957. 

 Although this species is obviously near to bairdi, and therefore very 

 near Ophioconis, it is easily distinguished from these allies by the 

 exposed radial shields, the characteristic mouth parts and the few 

 arm spines; the rounded tentacle scales are also different from those 

 of bairdi. 



OPHIACANTHA LOPHOBRACHIA, new species.a 



Disk about 4| mm. in diameter; arms about 15 mm. long. Disk 

 completely covered with a dense coat of short spines, which are thick, 

 and of nearly uniform height. Radial shields completely concealed. 

 Upper arm plates small, nearly triangular, somewhat wider than long, 

 well separated. Interbrachial spaces below apparently covered like 



FIG. 109. OPHIACANTHA LOPHOBRACHIA. x 12. a, FROM ABOVE; b, FROM BELOW; c, SIDE VIEW OF THREE 



ARM JOINTS NEAR DISK. 



disk. Genital slits short but wide. Oral shield nearly triangular 

 (madreporite, rhombic) longer than wide. Adoral plates very large, 

 wider without where they separate oral shield from arm plate than 

 within where they meet. Jaw terminated by a large, nearly triangu- 

 lar tooth, the lowest of the vertical series. On each side are three 

 oral papillae, narrow and spine-like. The outermost is much the 

 longest and is virtually a tentacle scale for the first oral tentacle, 

 which is very large. First under arm plate hexagonal, longer than 

 broad, widely separated from second, which is somewhat larger, pen- 



a A6<j>of signifying ridge, and {tpa%iiov, signifying arm, in reference to the unusually 

 notable ridges on the side arm plates. 



