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



fourth under plate. Genital opening bounded by small close-set papilla?. Disk thick. 

 Side mouth shields and under arm plates much swollen. Outer mouth papillae much 

 larger than inner. Genital papilla? large and bead-like. Six or seven small arm 

 spines. 



(Type specimen from Station 224.) Diameter of disk 12 mm. Width of arm, 

 without spines, close to disk 2 mm. Mouth papillae seven on each side, three basal 

 ones considerably largest; all forming a close line. Mouth shields small, triangular, 

 with acute angle inward, and outer edge much rounded. Side mouth shields large, 

 much longer than broad, wider without, meeting within; length to breadth 17:1. 

 Under arm plates from the second to the fourth or fifth furnished with tentacles ; 

 they are axe-shaped, with an angle inward, lateral sides re-enteringly curved, and 

 outer side curved ; beyond, the plates are rudimentary and diamond-shaped. Side 

 arm plates thick, meeting above and below beyond the disk. Upper arm plates 

 diamond-shaped, with an angle without and within ; length to breadth '7 : "7. Genital 

 scales long and narrow, bearing a row of papillae on the free edge. Lower interbrachial 

 space covered by thin curved plates, of which five form a transverse row along the disk 

 margin ; upper surface of disk pentagonal. Radial shields triangular, separated their 

 entire length by a row of small plates, and there is a similar row in each interbrachial 

 space ; the central space within the radial shields is covered by six circular primary 

 plates, separated by small ones. Arm spines six or seven in number, very short and 

 blunt, situated on the outer edge of the side arm plate. No scales beyond the fourth 

 or fifth under arm plate ; they are large, oval, and situated near the inner angle of the 

 plate, one to each pore. Colour in alcohol, grey. 



Station 224.— March 21, 1875; lat. 7° 45' N., long. 144° 20' E. ; 1850 fathoms; 

 globigerina ooze. 



Ophiortiusium cancellatum, Lym. (PI. II. figs. 16-18). 



Ophiomurium cancellatum, Lym., Bull. Mus. Comp. ZooL, vol. v., part 7, p. Ill, pi. L figs. 17, 

 18, 1878. 



Arms rather slender and tapering, cylindrical, or but slightly wavy. Upper and 

 under arm plates persisting nearly to end of arm, but no tentacles beyond third or fourth 

 under plate. Genital openings bounded by small close-set papillae. Disk flat, covered 

 with small imbricated scales, which are nearly equal, except the marginal, which 

 are larger. Upper arm plates large ; the basal ones long hexagonal. 



(Type specimen from Station 236.) Diameter of disk 8 "5 mm. Width of arm, 

 without spines, 1*5 mm. Length of arm 28 mm. Mouth papillae forming a close line, 

 six on each side, with one, diamond-shaped, at angle of jaw. Mouth shields triangular, 

 with an angle inward, sides equal and curved; length to breadth 1:1. Side mouth 



