150 THE VOYAGE OF H.M.S. CHALLENGER. 



Ophiocnida olivacea, Lym., Bull. Mus. Coinp. Zool., vol. i., part 10, p. 340, 1869 ; 

 111. Cat. Mus. Comp. Zool., No. vi., pi. i. figs. 7, 8 ; Bull. Mus. Comp. Zool, vol. v., 

 part 9, p. 227. 



West Indies ; 40 to 120 fathoms ; off Newport, Rhode Island; 86 to 126 fathoms. 



Ophiocnida putnami, Lym., 111. Cat. Mus. Comp. Zool., No. vi. p. 11, pi. i. 

 fig. 9, 1871. 

 Honsj Konsf. 



Ophiopus. 

 Ophiopus., Ljn., Viv. Of. Kong. Akad., 1866. 



Disk smooth and without spines, and covered by rather fine scales which separate the 

 rounded primary plates. Radial shields very small and somewhat widely separated. 

 Arms short and stout, with projecting side arm plates, which bear a few (three to four) 

 stout, regular spines. Mouth angles small and short bearing two flat papillae on either 

 side and a single one at the apex. Above the lateral papillae are one or two others. 

 Two genital openings in each interbrachial space. 



I am at a loss to separate this genus from some species of Ophiactis that have no disk 

 spines (e.g., Ophiactis canotia). The only character seems to be the presence of one or 

 two additional mouth papillae above the lateral ones, but these are perhaps only the 

 scales of the first pair of mouth tentacles. My friend Dr. Ljungman considers this 

 genus between Ophioglypha and Amphiura, but it would be hard to say what were its 

 affinities with the former. 



He informs me, in a recent letter, that Ophiaregma, G. O. Sars, is a synonym of this 

 genus, which leads to the inference that it has no genital openings. 



The presence or absence of genital openings among Ophiurans has not yet been fully 

 worked out. An observer is apt to take the crease in the disk, close to the arm, for a 

 true opening, while there may be none at all. 



In Ophiocymbmm and in Ophiothamnus I have not been able to detect any opening, 

 although the skin of that region was extremely thin and might readily be ruptured. 

 The situation is more puzzling in species covered by massive, strongly soldered plates, 

 such as Ophiomusium pidchettum, where I could detect no distinct opening ; and 

 Ophiomusium Jiabellum, whose side arm plates cover the whole interbrachial space and 

 seem to preclude the idea of genital openings. 



Species of 0}ihiop2<s not herein described. 



Ophiopus arcticus, Ljn., Oph. Viv. Of. Kong. Akad., p. 309, 1866. 



Ophiaregma abyssorum, G. O. Sars, Nye Echin, Vid. Selsk. Forh., p. 42, 1872. 

 Spitsbergen, Norway ; 400 fathoms. 



