ASTEEOTDEA OP H.M.S. ' CHALLENGEE, ' EXPEDITION. 239 



bouring segments. Ambulacral spines four to each, plate, short, 

 thin and compressed, uniform in breadth throughout and rounded 

 at the extremity, arranged in a straight, or sometimes slightly 

 curved, line and at a very slight angle to the furrow, the direction 

 of the line being outward from the furrow. A secondary row of 

 5 or 6 small granules stands on the outer margin of the adambu- 

 lacral plates behind the furrow-series, placed in a slightly curved 

 line ; and these become more or less indistinct along the outer 

 portion of the ray. 



The mouth-plates are large, prominent, and elevated along the 

 line of sutare ; the junction is imperfect, and the aboral extremi- 

 ties of the plates being widely open, expose the odontophore. 

 Mouth-spines 6 to 8 on each side, short, compressed and pointed : 

 the innermost one on each side larger and longer than the 

 rest, and directed towards the actinostome ; the lateral ones 

 falling into the furrow and interlocking with the corresponding 

 denticles of the neighbouring mouth-angle. A number (varying 

 from 6 to 12) of small granule-like tubercles are present on the 

 superficies of each plate; two, which are slightly largest, stand 

 near the inner third of the plate ; whilst the remainder are con- 

 fined to the aboral half of the plate, and are sometimes arranged 

 in two or three lines and sometimes irregularly. It seems 

 scarcely possible to rank these as secondary m outh- spine s ; and 

 yet there can be little doubt that they are rudimentary or 

 aborted representatives of these appendages. 



The ventral interbrachial areas are triangular in outline, and 

 covered with a regular plating of hexagonal imbricating scale- 

 like plates arranged in columnar series extending from the margin 

 to the furrow parallel with the median interbrachial line. The 

 plates are broader than long, the disproportion increasing as they 

 approach the margin ; they bear a few (3 to 5) small, widely- 

 spaced, irregularly disposed granules, some plates here and there 

 having none. 



Colour, in alcohol — margins and actinal area greyish white ; 

 dorsal membrane bluish grey, with touches of light brown near 

 the margin of the area and occasionally on the groups of paxillse 

 round the centre of the disk. 



Station 299. Lat. 33° 31' S., long. 74° 43' W. Depth 

 2160 fms. ; bottom temperature l°'l C. ; grey mud. 



Htphalastbr ineemis, n. sp. 



Marginal contour stellato-pentagonoid. E-ays five, well de- 



LINN. JOUEN. — ZOOLOGY, VOL. XTII. 18 



