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



nearly meeting without, broader without thaD within, where they touch. First under arm 

 plate small and three-sided, wider within than without ; those beyond are one-half broader 

 than long, with a curved outer side, and an irregular, more or less truncated angle within. 

 Side arm plates unusually wide, but not much projecting, nearly meeting above and 

 below. Upper arm plates much wider than long, three-sided, with a faintly curved outer 

 side, and an angle, sometimes truncated, within. Disk plentifully set with short, slender, 

 cylindrical spines, and covered with well rounded overlapping scales, which are large 

 above (two or three in the length of 1 mm.), and more regular and much smaller below 

 (four or five in 1 mm.). Radial shields sunken, rudely triangular, short and wide, 

 separated by a broad wedge of three or four large scales ; length to breadth 1*2 : 1. 

 Four cylindrical, tapering, blunt, rather stout arm spines, the two upper ones largest and 

 somewhat longer than an arm joint. One large, oval tentacle scale. Colour in alcohol, 

 pale straw. 



Station 174.— August 3, 1874; lat. 19° 10' S., long. 178° 10' E. ; 210 to 610 

 fathoms ; globigerina ooze. Station 171.— July 15, 1874 ; lat. 28° 33' S., long. 177° 50' 

 W. ; 600 fathoms. 



Opluactis Mrta, Lym. (PI. XX. figs. 4-6). 



02>hiactis hirta, Lym., Bull. Mus. Ccrnnp. Zool., vol. vi., part 2, p. 39, pi. xiii. figs. 365-367, 

 1879. 



Disk finely scaled, and set with short minute spines. Eadial shields small and pear- 

 seed shaped. Four moderately stout tapering arm sj3ines, the uppermost longest. Two 

 or three minute mouth papilla? on each side. Seven arms. 



(Type specimen from Station 164a.) Diameter of disk 4*3 mm. Length of arm about 

 1 4 mm. Width of arm near disk 1 "2 mm. Two or three small, narrow, scale-like mouth 

 papillaa on either side of the very narrow mouth angle ; and one wide, flat, and pointed at 

 the apex ; this last may, as in all similar cases, be considered the lowest tooth. Mouth 

 shields small, of a much rounded diamond shape ; sometimes nearly circular. Side mouth 

 shields narrow, of nearly equal width, meeting within. Under arm plates rather small, as 

 broad as long, bounded without by a strong curve, and within by three sides of an octagon. 

 Side arm plates stout, projecting laterally in a well-marked spine ridge, meeting neither 

 above nor below. Upper arm plates a little broader than long, transverse oval, with the 

 inner sides more or less angular. Disk covered with coarse, thickened, irregular scales, 

 those of the under surface being sometimes wholly obscured by a thick skin ; those in the 

 centre are largest, but the primary plates are not readily distinguishable ; there are 

 small, peg-like spines scattered over the entire surface. There are seven pairs of radial 

 shields, which are small, sunken below the disk surface, of a blunt pear-seed shape, and 

 separated by a rather wide wedge of three scales. Four smooth, rounded, tapering, 

 moderately stout arm-spines ; the upper one longest ; lengths to that of an under arm 



