RAYS. 



341 



Of all the genera of Batoidei, Eays have the widest 

 geographical range ; they are chiefly inhabitants of temperate 





Fig. 126. — Raja lemprieri, from Tasmania. 



seas, and much more numerous in those of the Northern than 



of the Southern Hemisphere. They advance more closely to 



the Arctic and Antarctic circles than any other member of 



this group. More than thirty species are 



known, of which the following are found on 



the British coast : — The Thornback {R. ela- 



vata), the Homelyn Eay {R. maculata), the ■ 



Starry Eay {R. radiata), the Sandy Eay {R. 



circularis), the common Skate {R. hatis), the 



Burton Skate (R. marginata), and the Shagreen 



Skate {R. fullonica). Some of these species, 



especially the Skates, attain a considerable size, ^'^■. ^'^'^ — Dermal 



'■ •' _ spmes of a male 



the disk measuring six and even seven feet Thomback, Raja 

 across. All are eatable, and some of them <=iavata. 

 regularly brought to market. In the majority of the species 

 peculiar sexual differences have been observed. In some, 

 as in the Thornback, all or some of the teeth are pointed in 

 the male sex, whilst they are obtuse and fiat in the female. 

 The males of all are armed with patches of claw-like spines, 

 retractile in grooves of the integument, and serially arranged 

 occupying a space on the upper side of the pectoral fin 



"^ji^ 



