EAYS. 



345 



each side. Tail very long and thin, with a dorsal fin near its 

 root ; generally a serrated spine behind the fin. 



Seven species are known, two of which are European, one 

 (if. aquila) being almost cosmopolitan, and occasionally 

 found on the British coast. The young differ much from 

 the adult, having no median series of larger teeth, but all the 

 teeth of equal size and regularly sexangular. Also the tail is 

 much longer in young examples than in old ones, and the 

 coloration more ornamental. Teeth of species very closely 

 allied to, or perhaps even identical with, existing species, are 

 found in tertiary formations. 



Aetobatis. — Form of the head, body, and tail as mMyliohatis. 

 The nasal valves remain separate, each forming a long flap. The 

 lower dental lamina projects beyond the upper. Teeth flat, 

 broad, forming a single series, equivalent to the median series of 

 Myliobatis, there being no small lateral teeth. 



Fig. 130. — Aetobatis narinari. 



One species only (A. narinari) which is found in almost 



