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



Both this genus and Ophionephthys are apparently naked over most of the disk. It 

 may be, however, that a minutely squamous coat is hidden under the integument. 



Species of Ophionenia not herein described. 



OpUonema intricata, Ltk., Addit. ad Hist., part 3, pp. 27, 98, 1869. 

 West Indies. 



Ophionephthys. 



Ophionephthys, Ltk., Addit. ad Hist., part 3, 1869. 



Disk small, delicate, and a little puffed, and having long, slender, even arms. Its 

 skin is apparently quite naked, except where there are rows of scales about the radia. 

 shields, or along the margin. The mouth angles are small and short, and bear a few 

 (four to six) small mouth papLUaj. Four or five small arm spines. Two genital openings 

 in each interbrachial space. 



Species of Ophionephthys not herein described. 



Ophionephthys limicola, Ltk., Addit. ad Hist., part 3, pp. 25, 98, 1869. 

 West Indies. 



OphioJiephthys phalerata, Lym., Bulk Mus. Comp. Zook, vol. iii., part 10, p. 229, 

 pi. vi. figs. 7-9, 1874. 

 Philippines. 



Ophiocnida. 



Ophiocnida, Lym., HI. Cat. Mus. Comp. Zool., No. i., 1865. 



Disk small and delicate, furnished with uncovered radial shields, its coat of naked, 

 overlapping scales is beset with small thorns or grains. Teeth. No tooth papillae. 

 Mouth angles short and small, bearing a few (four to six) little mouth papillae. Arms 

 long, slender, even, more or less flattened. Arm spines short and regular. Two genital 

 openings in each interbrachial space. 



0])hiocnida is Amphiura beset with small spines or grains, just as Op)hiactis is 

 Amphiura of a very robust structure with short wide arms. The three genera differ 

 within themselves very much, and shade into each other on their borders ; and they are 

 almost as closely allied with OphiophoUs, Ophionema, Ophionephthys, Amphilepis, &c., 

 as with each other. But, while as genera they are difficult to define, the species within 

 the genera are curiously constant, well marked, and unvarying. In this they contrast 

 with such a genus as Ophiothrix, well and clearly set off from its neighbour Ophiooiemis, 

 but having species which are almost impossible of distinction. 



