REPORT ON THE OPHIUROIDEA. 209 



the scales are smaller and obscured by skin. Eadial shields small, ovoid, as long as 

 broad, widely separated by a wedge of scales; length to breadth, 1"7 : 1'3. Genital 

 openings wide, and extending quite from the mouth shield to the disk margin. Four 

 smooth, cylindrical, rather slender, blunt, tapering arm spines, whereof the lowest is as 

 long as an arm joint, the two upper ones as long as a joint and a half, and the third 

 intermediate. One rather large oval tentacle scale. Colour in alcohol, grey, with arm 

 inclining to straw. 



Station 232.— May 12, 1875 ; lat. 35° 11' N., long. 139° 28' E. ; 345 fathoms ; sandy 

 mud. Station 235.— June 4, 1875; lat. 34° 7' N., long. 138° 0' E. ; 565 fathoms; 

 mud. Station 236.— June 5, 1875 ; lat. 34° 58' N., long. 139° 30' E. ; young; 420 to 

 775 fathoms; mud. 



Species of Oiyhiomitra not herein described. 

 Opliiomitra valida, Lym. (PI. XLI. figs. 4-6). 



OpMomitra valida, Lym., BuU. Mus. Comp. Zool., vol. i., j)art 10, p. 325, 1869; 111. Cat. 



Mus. Comp. Zool., No. vi., pL ii. figs. 4-6. 

 Opliiomitra cervicornis (young form), Lym., lU. Cat. Mus. Comp. ZooL, No. viii., part 2, p. 14, 



pi. ii. figs. 19, 20, 1875; Bull Mus. Comp. ZooL, vol v., part 9, p. 231. 



West Indies ; 10 to 128 fathoms. 



Opliiomitra exigua, Lym., Bull. Mus. Comp. Zool., vol. v., part 9, p. 231, pi. i. figs. 

 4-6, 1878. 



Off Havana ; 240 fathoms. 



OpMocamax. 



OpMocamax, Lym., Bull Mus. Comp. Zool., vol. v., part 7, 1878. 



Seen from within the radial .shields are even larger than they appear from without. 

 Near their outer point of junction are attached genital plates which are peculiar in that 

 their inner ends lie on top of the arm and nearly touch each other, while their very thin, 

 blade-like shafts slope downwards and inwards to the sides of the arms. Also attached 

 to the radial shield are the curved, thin genital scales (PI. XLI. fig. 9, n). The arm 

 next the mouth frames is very large and wide, and its bones are strong, with wide, 

 slio'htly grooved margins. Their faces are of a character wholly unlooked for, recalling 

 the remote Astrophyton shapes. Thus, the outer face has no articulating peg at aU and 

 the articulating hollow above (fig. 10 : 4) is formed by a transverse hour-glass piece, the 

 whole quite comparable to such a remote genus as Sigsheia (PI. XLIII. fig. 5). The inner 

 face is of a character much more Ophiuroid (PI. XLI. fig. 11), and is comparable to that 



