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



which are broad, heart-shaped, with a peak within. Mouth shields wider than long, broad, 

 heart-shaped, with a rounded angle within, or wide transverse, rounded diamond-shaped. 

 Side mouth shields rather narrow, of about equal width, meeting fully within. First 

 under arm plate small and wider within than without ; those beyond are wide shield- 

 shaped, bounded without by a curve, on the lateral sides by re-entering curves, and 

 within by an obtuse or truncated angle. Side mouth shields of moderate width, nearly 

 meeting above and below, and having a well-marked spine crest. Upper arm plates 

 broad, transverse diamond-shaped, with outer and inner angles rounded. Disk covered 

 with rather thick overlapping scales, which are finest below, near the mouth shields, 

 where there are about seven in the length of 1 mm. Above, the centre is occupied by a 

 rosette of two circles of large rounded plates partially separated by a few small scales. 

 Radial shields short, wide pear-seed shaped, separated their entire length by a narrow 

 wedge of three scales. On interbrachial spaces below, a few minute, peg-like spines. 

 Four short, cyhndi-ical, tapering, blunt arm spines, all stout, especially the lower ones ; 

 upper spine longest, and about as long as one and a half joints. One large oval tentacle 

 scale. Colour in alcohol, pale straw. 



Station 73. -June 30, 1873 ; lat. 38° 30' N., long. 31° 14' W. ; 1000 fathoms; globi- 

 gerina ooze. 



OiMactis earned, Ljn., Oph. Viv. Of. Kong. Akad., p. 324, 1866. 

 Station, Simon's Bay, Cape of Good Hope ; 10 to 20 fathoms. 



Ophiactis pectorah, Lym. (PI. XXVII. figs. 4-6). 



OpMaetis pectorale, Lym., Anniv. Mem. Bost. Soe. Nat. Hist., p. 10, pi. ii. figs. 26-28, 1880. 



Disk without spines, and covered with thick, rounded scales, whereof the largest are 

 near the radial shields. Two small tentacle scales. 



Diameter of disk, 7 mm. Length of arm about 38 mm. Width of same, close to 

 disk, without spines, 2 mm. Three large, flat, irregular mouth-papillse on either side of 

 the mouth angle ; and one long, thick, blunt papilla, or tooth, at the apex. Mouth 

 shields slightly swollen, wide diamond-shaped, with rounded angles and a slight lobe 

 without; length to breadth, 1:1. Side mouth shields short, wide and of nearly equal 

 width, meeting fully within. First under arm plate small, longer than wide, five- 

 sided with rounded angles and curved outer edge ; beyond, the plates are much broader 

 than long, with an ill-marked angle within, shoit deep re-entering curves on the lateral 

 sides, and outer side long and cleanly curved. Side arm plates short ; narrowly 

 separated above and below. Upper arm plates much wider than long, thick, slightly 

 arched, with a broad rounded angle within, acute angles on the lateral sides, and outer 

 edge gently curved. Disk thick, having deep radiating constrictions in the interbrachial 

 .spaces, extending even to the centre ; it is covered with large, thick, flat, rounded, over- 



