G13 THE VOYAGE OF H.M.S. CHALLENGER. 



1. Freyella pennata, n. sp. (PL CXI. figs. 1-4). 



[lays ton. E = 200 to 240 mm. ; r = 11 mm. P>20 r. Breadth of a ray at the base, 

 6 mm. ; at the widest part of the ovarial expansion 10 to 11 mm., this latter dimension 

 being situated at about 15 mm. from the place of junction with the disk ; midway 

 between the base and the extremity the breadth of the ray is 4'5 mm. 



Pays of great length, delicate, subcarinately cylindrical (or, perhaps, more correctly, 

 subtriangular and truncate along the median line), slightly constricted at the base and 

 narrow for a short distance scarcely equal to twice the breadth and then expanding rather 

 abruptly into a fusiform ovarial inflation, which gradually contracts and the ray from 

 thence tapers regularly to the extremity. 



The disk is small, elevated rather abruptly above the level of the rays at their base, 

 with the abactinal surface subplane and undulating. The small narrow portion of the ray 

 which intervenes between the disk and the ovarial swelling is cylindrical, and a longi- 

 tudinal section through the median radial line would exhibit a rather deep concavity 

 between the disk and the swelling, the descent being more rapid near the former than the 

 latter. The lateral wall of the disk in the interbrachial arcs is vertical. The disk and 

 the basal portion of the rays for some distance beyond the ovarial swelling are covered 

 with a fleshy membrane through which protrude a number of very minute, delicate, 

 uniform, pointed spinelets, so small that the spiniferous membrane as a whole only presents 

 an appearance to the naked eye suggestive of a rather coarse velvet pile. When examined 

 microscopically the membrane is found to be underlaid by a pavement of thin, delicate, 

 irregularly suboval, imbricating calcareous plates, each of which bears from two to four 

 small, cylindrical, tapering, pointed spinelets - 6 to 0'8 mm. in length and a few small 

 crossed pedicellarise (about six or eight). The spinelets, which are of very simple structure 

 and built up of not more than three or four outer rods, with scalariform dissepiments, are 

 enclosed in a membranous sheath, the thickness of the invested spine being about 0'133 

 mm., and the thickness of the calcareous spine alone about - 066 mm. near the base. The 

 pedicellarise, which are sessile and of the characteristic form found on Brisingidse generally, 

 arc very small, a closed pedicellaria not measuring more than 0"135 mm., from the base 

 to the apex of the valves. The pavement plates are of extreme' delicacy, presenting a 

 single layer of extremely fine calcareous network, the meshes having a diameter of about 

 0-022 mm., and rarely a few are slightly larger. This spiniferous, plate-paved mem- 

 brane extends uninterruptedly and uniformly over the disk and along the basal portion of 

 the rays for a distance of about 50 mm. from their attachment to the disk, in fact as far 

 as the generative organs reach. From this point an exceedingly delicate membrane with- 

 out plates covers the ray up to the extremity. This membrane is so fine and transparent 

 that the ambulacral ossicles of the ray are clearly visible through it, indeed its presence is 

 not at first sight detected, and the rays have the superficial appearance of being denuded 

 of membrane beyond the point where the spiniferous membrane of the ovarial regions 



