RAYS. 317 



torals are here greatly extended in breadth in 

 proportion to their length, giving to the fish 

 somewhat of the outline of a bat or a butterfly, 

 dilated to gigantic dimensions. The anterior 

 half of the head is free, and the eyes are placed 

 at the margin of its summit. The teeth are 

 arranged like broad flat paving stones, of regular 

 forms : the tail is still more lengthened and at- 

 tenuated than in the last sub -family, and is fur- 

 nished with a serrated spine ; it has a small 

 dorsal near its base. Two species of this group 

 are British, though very rare ; one of these is 

 the Cephalopteray already mentioned as attaining 

 colossal proportions, and displaying a fierce vo- 

 racity in the tropical seas. 



Genus Raia. (Linn.) 



In this the most numerous genus of the 

 Family, and the only one of any value to man, 

 the disk is rhomboidal, greatly flattened ; the 

 tail is moderately slender, generally armed with 

 rows of small spines ; there is no notched spear, but 

 two small dorsals near the tip are present^ and 

 sometimes the vestige of a caudal ; the teeth are 

 flattened, small, arranged in quincunx, the cen- 

 tral ones becoming lengthened and pointed with 

 age. The head and neck cannot be externally 

 distinguished from the body, being included on 

 the sides by the fore-part of the pectorals. The 

 body is in general beset with sharp points, or 

 spinous tubercles, sometimes small and few as 

 in the Skate {Raia batis, Linn.) ; sometimes 

 large and numerous as in the Thornback {R. 

 clavata). 



