646 THE VOYAGE OF H.M.S. CHALLENGER 



traced as far as 28 mm. from the base. The outer part of the ray is covered with a very 

 delicate semitransparent membrane. 



The ambulacra! furrow is wide and measures 1*6 mm. at a part where the ray is 

 2*5 mm. The adambulacral plates are remarkable for their length and generally 

 attenuate character. Indeed the same remark applies to the whole ambulacral ossicle or 

 segment, the latter when seen from above having the appearance of two thin cylindrical 

 rods placed side by side. The length of the adambulacral plate is 2 - 8 mm. at 25 mm. 

 from the base ; its furrow-margin is deeply concave, and the outer margin to a less degree, 

 the shape of the plate being that of an elongate phalangial bone considerably constricted 

 in the median region; when seen from the actinal side it has also a slightly angulated 

 or twisted appearance in consequence of the posture and formation of the tubercle upon 

 which the actinal spine is articulated. The plates overlap considerably, the aboral end 

 of one being hollowed out to receive the produced adoral end of the next plate, and a 

 rather wide space between is occupied by ligament. The adambulacral armature consists 

 of: — (1.) a very minute inner spine directed over the furrow, but which is present only on 

 the extreme basal portion of the ray ; (2.) a short actinal spine, articulated on a rudi- 

 mentary infero-marginal plate on the actinal surface of the plate ; (3.) a short delicate 

 lateral spine articulated on the lateral margin of each alternate plate. The small inner 

 spine, excepting on the first one or two segments, is quite microscopic, thornlike and 

 sharply pointed, and deeply placed in the furrow, near the aboral extremity of the plate, 

 and covered with membrane, upon which I find no trace of any pedicellarise. The actinal 

 spine is small, about 2 mm. in length, very delicate, tapering to a sharp point, and 

 encased in a thin membranous sheath, crowded with small pedicellaria?, which develops a 

 rather elongate sacculus at the distal extremity. Notwithstanding its small size this 

 spine has a large expanded condyloid base by which it is articulated on a prominent 

 tubercle situated slightly on the aboral side of the median point of the actinal surface 

 of the adambulacral plate. The lateral spine is extremely delicate, about 6 "5 mm. in 

 length, and is encased in a thin membranous sheath, with an elongate saccular extension 

 at the distal extremity, and covered with numerous small pedicellarise. It resembles 

 the actinal spine in the character of its base, and is articulated on a prominent tubercle- 

 like rudimentary infero-marginal plate, ankylosed on the lateral margin of the adam- 

 bulacral plate in a line with the tubercle that bears the actinal spine. 



Colour in alcohol, a delicate pellucid white, with a fleshy shade on the ovarial region. 



Locality. — Station 226. West of the Mariana or Ladrone Islands. March 25, 1875. 

 Lat. 14° 44' 0" N., long. 142° 13' 0" E. Depth 2300 fathoms. Eadiolarian ooze. 

 Bottom temperature 35°-5 Fahr. ; surface temperature 79°"0 Fahr. 



Remarks. — At first sight I was disposed to think that possibly this might be the 

 young form of Freyella heroina, to which it is most nearly allied, but when the extra- 

 ordinary length and attenuation of the ray segments, greater than that found in any part 



