230 ME. W. PERCY SLADEN OK THE 



portion of the disk slopes downwards, with an inward bending 

 curve from the margin to the mouth-plates, producing a very 

 prominent convexity on the under surface. 



Marginal plates deep and almost vertical. Along the whole 

 of the ray beyond the disk the supero- marginal series of either 

 side meet, and, from being bent inwards very slightly, produce 

 the laterally compressed and high-arched character of the ray. 

 The supero-marginal series are 23 in number on one side of a 

 ray, and all the plates are longer than high. Along the whole 

 of the free portion of the ray each alternate supero-marginal 

 plate bears a long sharply -pointed spine on its upper edge ; 

 and the spine-bearing plates of the two sides of a ray alternate, 

 the unarmed plate of the one side corresponding to the armed 

 plate of the other ; hence it follows that a straight single line of 

 vertically directed spines extends along the whole of the median 

 dorsal line. The spines are robust at the base, conical, and 

 taper to a very finely pointed extremity. The spines are longer 

 than the depth (height) of the ray, and they normally decrease 

 in size as they proceed outwards ; but the regularity of this is 

 sometimes broken by the occurrence of a shorter spine here and 

 there. The spines are slightly curved in the plane of the direc- 

 tion of the ray, the point turning outwards. Occasionally a 

 small additional spine is intercalated here and there in the 

 otherwise equally spaced series, in consequence of the corre- 

 sponding plates of the two sides of the ray each bearing a spine. 

 The terminal plate is rather large, compressed, and elongate, its 

 dorsal surface sloping upwards at an angle of 45° from the 

 general dorsal line of the ray, and its ventral surface is rounded, 

 thereby emphasizing the character of the upturned tip of the 

 ray. The terminal plate bears three sjjines — one at the extremity 

 in the prolongation of the median dorsal line, and one on either 

 side at a lower level on the furrow -margin, all quite at the ex- 

 tremity and close together. In a large specimen an additional 

 spine is present, larger than the terminal dorsal one, and placed 

 behind it in the median doi^sal line of the plate. 



The infero-marginal plates are much shallower than the 

 superior series, their length being nearly twice their height. In 

 large specimens they frequently alternate, instead of corre- 

 sponding, with the companion infero-marginal, especially on the 

 outer part of the ray ; and sometimes an intermediate lateral 

 series of plates, almost as large as the infero-marginals, is inter- 



