C28 THE VOYAGE OF II.M.S. CHALLENGER. 



than broad, but are relatively sborter than in many species of Freyella and Brisinga. 

 They measure 1*5 mm. in length at about 70 mm. from the disk, and form a robust-looking 

 margin to the furrow. They are narrower midway between their extremities, and the 

 furrow-margin of the plate is the most incurved, though the concavity is by no means 

 great. The adambulacral armature consists of : — (1.) a small inner spinelet directed over 

 the furrow ; (2.) a large perpendicular spine on the actinal surface ; and (3.) a lateral spine, 

 normally on alternate plates. The small inner spine is attached to the extreme aboral end 

 of the furrow-margin of the plate, and is directed nearly horizontally over the furrow, and 

 at a slight au<de forwards : it is about 1 mm. in length, and is covered with a delicate and 

 rather loose membranous sheath somewhat saccular at the extremity, and bearing a 

 number of very small pedicellarise near the distal' extremity chiefly. The perpendicular 

 spines are about 4 mm. in length at 35 mm. from the disk, and articulated on a prominent 

 tubercle rather away from the centre of the actinal surface of the plate towards the aboral 

 extremity ; they are encased in a delicate semitransparent membranous sheath, covered 

 with great numbers of very small pedicellariae, but scarcely so crowded as in some species ; 

 the sheath is more or less prolonged at the extremity and a slight saccular expansion is 

 present there. The lateral spine, like the foregoing, appears to be articulated on a promi- 

 nent tubercle, but it is in reality a rudimentary infero-marginal plate ankylosed on the 

 lateral surface of the adambulacral plate and nearer the aboral end than the middle. The 

 spine is very delicate and needle-like, 11 mm. in length at about 50 mm. from the disk, 

 and 13 mm. at 75 mm., and the longest, a little further outward, is less than 1 mm. more ; 

 it is encased in a delicate membranous sheath, on which are crowded very miuute pedi- 

 cellariae, but scarcely so numerous as in other species ; the extremity of the sheath is 

 slightly prolonged and saccular. The character of the spinulation of the ray as a whole 

 may be said to be comparatively short and delicate, and the spines appear to be much 

 more numerous and more closely placed than in many others in consequence of the relative 

 shortness of the ambul acral segments. Respecting these latter it may be here remarked 

 that the part of the ambulacral plate which unites with the companion plate and forms 

 the prominent keel along the median abactinal aspect of the ray is strikingly vertebra-like 

 in form, the median portion being deeply incurved, with the adoral and aboral extremities 

 of this surface higher and more prominent than usual in other species. 



The actinostome occupies nearly the whole of the actinal area of the disk, its diameter 

 being 13 mm. in a disk 19 to 20 mm. in diameter. The buccal membrane is thick and 

 opaque, and remarkable for its surface being covered with papilliform villous appendages, 

 rather widely spaced, nearly as long as the spinelets on the abactinal surface, and with 

 slightly claviform extremities. They are of unequal size, however, and the largest are 

 near the margin of the mouth. The mouth-plates are small and very insignificant. The 

 united pair are subquadrate in form, the adoral margin being almost straight, the lateral 

 margins straight and slightly converging, causing the adoral margin to be a little less 



