435 



Fam. 4. RAJID.E. 



Disk broad, rhombic, generally rough ; tail with a louptxidiaal 

 fold on each side. Pectorals extending to the snout. No electric 

 organ. No serrated caudal spine. 



Caudal fin rudimeutary or absent ; each ventral deeply notcliod. 



11. llujd, p. 455. 

 Pectorals contJucnt in front of the snout ; each ventral deeply notched. 



12. Psanunvbatis, p. 470. 

 Caudal fin rudimentary ; pectorals confluent in front of the .=nout ; ven- 



trals without notch 1.3. Si/mptcnmia, p. 470. 



Caudal fin well developed 14. PUttyrhiad, p. 470. 



Fam. 5. TRYGONID.^. 



Pectoral fins uninterruptedly continued to and confluent at the 

 extremity of the snout. Tail without lateral longitudinal folds. 



* Tail ivitJiout serrated sjiiiie. 



Tail long 15. UrogymnKs, p. 471. 



Tail short, with strong spinous exci'escences round the basal portion. 



IG. EUipcswus, p. 472. 

 ** Tail tvith a barbed spine. 



Tail long, fiuless, sometimes with a cutaneous fold below, which does not 

 extend to its extremity 17. Try yon, p. 472. 



Tail with a rayless cutaneous fold b-ilow, which extends to its extremity. 



18. Taniura, p. 483. 



Tail with a distinct rayed terminal fin 19. Urolophiis, p. 485. 



Tail very short, without terminal tin ; bodv at least twice as broad as 

 long- '. . 20. Ptcroplatea, p. 48G. 



Fam. 6. MYLIOBATID.E. 



Sides of the head free from the pectoral fins ; snout with a de- 

 tached pair of cephalic fins. 



A. TeetJi large, flat, tessellated Myliobatina. 



The cephalic fins form a soft appendage in front of the snout. Teeth in 

 several series, of which the middle contains very broad teeth. 



21". Myliohatis, p. 48.S. 



Only one series of very broad teeth 22. A'etobatis, p. 402. 



The" cephalic fins separate, and forming a pair of lobes at the lower side of 

 the snout 23. Ehinoptcra, p. 493. 



B. Teeth ver II small ; cephalic flns forming a pair of separat, appen- 



dages in front of the snout Ceratopterina. 



Teeth in both jaws 24. DiciTohatis, p. 49t). 



Teeth in the lower jaw (inly 25. Ccrati>ptera, 4D7. 



2 t2 



