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



Ophiolehes humilis, Lym. 



Ophiadis humilis, Lym., Bull Mus. Comp. Zool., vol. i., part 10, p. 329, 1869. 

 Florida; 125 to 324 fathoms. 



Ophiomitra. 

 Opliiomitra, Lym., BuU. Mu.s. Comp. Zool., vol. i., part 10, 1869. 



Teeth. Numerous (7-11) small, nearly equal mouth papillse. No tooth papillae. 

 Disk flat, cii'cular, and erect, covered with scales and wide radial shields, and beset with 

 thorny spines or stumps. Arm spines rough. Side arm plates large and nearly or 

 quite meeting above and below, two genital openings in each interbrachial space. 



So far as concerns the arms and the chewing apparatus, this is an Ophiacantha ; 

 but the disk, with its large naked scales and broad radial shields, separates it from that 

 genus, which is characterised by the long, very narrow, radial shields, covered, together 

 with the disk, by a thin skin bearing more or less thorny appendages. 



In typical species {Opjhiomitra valida) the arm spines are solid, like those of 

 Ophiocamax ; but others {Ophiomitra chelys) have them hollow, like Ophiacantha. 

 The radial shields are always large and wide, sometimes flat {Ophiomitra valida) at 

 others countersunk in a sort of fold {Ophiomitra chelys). The strong mouth angles have 

 a thick, single, swollen peristomial plate (removed in PI. XLI. fig. 4), which covers a 

 very deep nerve ring {u). The genital plate is short and club-like, with a short, 

 curved, blade-like scale. This scale in Ophiomitra chelys is short, straight, and rounded. 

 The first free arm bone has a lozenge-shaped top, with a sunken centre {w'). On their 

 outer face, the arm bones, which are much wider than long, have very prominent ten- 

 tacle sockets (fig. 5r), while the inner face has flat wings and a prominent umbo (fig. 6). 



See Plate XLI. figs 4-6. 



o 



Table of Species of Ophiomitra. 



Nine rougli, stout, solid arm spines. Disk evenly covered with large radial shields 1 



J ,,,.,,., , (■ Ophiomitra valida. 



and scales, beset with thorny stumps, . . . . . . ) 



Six smooth, short, tapering arm spines. Upper disk bearing a few thorny stumps, ) . . 



and covered almost whoUy by the large radial shields, . . . . J '^P^'-^omitra exigua. 



Four smooth, slender, solid arm spines. Disk sparsely granulated, . . . Ophiomitra nonnani. 



Five to six stout arm spines. Outer edge of under arm plate swollen, and in large ) 



. J 1 1" Ophiomitra plicata. 



specimens turned down, . . . . . . . ■ j r ■ 



Eight arm spines, less stout than in preceding. Tentacle scales thorny, . . Ophiomitra sarsii. 



Six arm spines ; under one thickened or bent. Eadial shields widely separated, . Ophiomitra clichjs. 



Six arm spines ; the under one straight. Tentacle scales thorny. Under arm spine 1 . . 



, -^i , } Ophiomitra carduus. 



Six arm spines, the two uppeimost very long and slender. Marginal disk plates large ) 



and much swollen. Central disk scales smaU, ] Ophiomitra dipsacos. 



