LIST OF FISH. 85 



3. Rhinoptera. — Head naked ; teeth six-sided ; ventral larger. 



4. jElobates. — Head entire; mandibles produced beyond the 

 maxilla ; nasal-valve deeply cut; teeth in one series. 



5. Myliobates. — Head entire ; nasal-valve truncated ; teeth cen- 

 tral, large ; lateral small, in many series. 



3. Head enclosed by the pectoral-fins ; teeth small, in quint-uncial 

 order. — Raiana. 



A. Acanthini. — Tail slender, fin/ess and armless. 



6. Urogymnus. — Lower caudal-fin narrow. 



7. Anacanthus. — Tail finless. 



B. Trygonini. — Tail slender, with a strong doubly serrated spine. 



8. Urolophus. — Tail-fin terminal ; teeth tesselliform. 



9. Hypolophus. — -Teeth hexagonal, in centre of maxilla very 

 small, at the sides larger ; lower caudal-fin very broad. 



10. T.kniura. — Teeth acute, base elliptical; mouth waved; 

 margin of the jaws exerted, each cultriform ; lower caudal-fin sub- 

 apical ; upper none. 



11. Pteroplatea. — Teeth one or three, cuspid; body broader 

 than long; tail shorter than the body. 



12. Himantura. — Teeth elliptical, transversely keeled; dorsal- 

 fins none. 



13. Hemitrygon. — Teeth elliptical, transversely keeled ; upper 

 dorsal-fins none. 



14. Trygon. — Teeth elliptical, transversely keeled; upper and 

 lower dorsal -fins distinct. 



C. Raini. — Tail elongate, ivith two dorsals ; body rhomboidal. 



15. Uraptera. — Caudal none; pectoral-fins hardly produced 

 beyond the middle of the beak ; veutrals two-lobed. 



16. Sympterygia. — Caudal distinct; pectoral-fins produced be- 

 yond the middle of the beak, attaining the ; ventrals one- 



lobed. 



17. Raia. — Caudal-fin distinct ; pectoral-fin hardly produced be- 

 yond the middle of the beak ; ventrals two-lobed ; beak acute. 



