RAYS. 
317 
torals are here greatly extended in breadth in 
proportion to their length, giving to the figh 
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-fainily, 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 Cephaloptera, already mentioned as attaining 
colossal proportions, and displaying a flerce 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 hatis, Linn.) ; sometimes 
large and numerous as in the Thornback {R, 
clavata). 
