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



teeth, which are sometimes almost spiniform, but usually flattened. Mouth shields 

 much wider than long, with a well marked obtuse angle inward and the outer side gently 

 curved; length to breadth, 7 : I'l. Side mouth shields long, rather narrow, of nearly 

 equal width, slightly curved, and fully meeting within. First under arm plate small, 

 lono-er than broad, hexagonal, with rounded corners ; the plates beyond are rather small, 

 wider than long, bounded without by a broad curve, and within Ijy an obtuse angle ; the 

 lateral sides are very short, or are confounded in the outer curve. Side arm plates small, 

 somewhat wider than long, fan shaped, with inner angle rounded. Disk rather thick, 

 finely and uniformly granulated above and below, about seventeen grains in the length 

 of 1 mm. Four cylindrical, tapering, rather slender arm spines, whereof the uppermost 

 is longest : lengths to that of an arm joint, I'l, '6, "5, "4 : '6. One small, narrow tentacle 

 scale. Colour in alcohol, straw. 



Station 320.— February 14, 187G; lat. 37° 17' S., long. 53° 52' W. ; GOO fathoms; 

 hard srround. 



Species of Opliiocliondrus not herein described. 



Ophiochondrus convolutus, Lym. (PI. XLIII. figs. 11-15). 



Upluochondnis convolutii!<, Lym., Bull. ]\Ius. Comp. ZooL, vol. i., part 10, p. 328, 1869 ; 11. Cat. 

 Mus. Comp. ZooL, Xo. vL, pi. ii., fig. 7 ; Bull. Mus. Comp Zool., vol. v., part 9, ji. 22.3. 



West Indies ; 175 to 292 fathoms. 



IlehueurijaJe. 

 Hemieiiri/ale, V. Mart., Jlonatsb. Ivonig. Akad. Berlin, 1867. 



Teeth. Numerous small crowded mouth papilla3. No tooth papilla?. Disk small and 

 covered with scales and large swollen radial shields. Arms long, and rolling in a vertical 

 plane, furnished with under and side arm plates of the ordinary form, but covered above 

 by a mosaic of small, swollen plates, whereof one, much larger and higher than the rest, 

 is on each side of the arm. Two short genital openings in each interbrachial space. 



Here is another solid structure comparable to Ophiochondrus. The great radial shields 

 with their thickened margins occupy almost the entire upper disk (PI. XLIII. fig. 7). 

 To each is jointed a massive, shapeless genital plate (o) extending quite to the mouth 

 shield, and which has soldered to it a small genital scale (h). The mouth angles are 

 compact, and the mouth frames (/) scarcely flaring over the nerve ring is a small, single, 

 rounded peristomial plate [o). Beyond the disk the arm bones are elongated, much as in 

 Ophiochondrus (fig. 10), and, in profile, exhibit an umbo (l) projecting from the hinder 

 end, and a still larger articulating shoulder from the outer end ; while l)elow are large 



