SYNOPSIS OF FAMILIES. 259 



Narcoidei. 



Disk broad, including an electric battery at each side of head 



copula incomplete; nasoral grooves present; pectorals widely separated 

 prepelvic processes lateral; rostral cartilages branching 



Narcaciontidae (page 293) 



Raioidei. 



Disk broad, not including an electric battery; nasoral grooves present 

 copula unsegmented; pectorals not meeting in front; no caudal spine 

 prepelvic processes lateral; rostral cartilage present or absent 



Raiidae (page 316) 



Dasybatoidei. 



Disk broad; no electric organs; tail slender, with, or rarely without a spine 

 nasoral grooves 

 copula segmented; pectorals extended to end of snout; no median rostral 

 cartilage 

 prepelvic process median, rudimentary . Dasybatidae (page 373) 

 copula segmented; pectorals reaching end of snout; no rostral cartilage 

 prepelvic process median, elongate; disk subcircular to elliptic 



Potamotrygonidae (page 415) 



Myloidei. 



Disk polygonal, pectorals broad angular; copula imperfect; no rostral cartilage 

 snout in a single lobe; teeth broad, molarial; nasoral grooves 



prepelvic process median, rather short; pelvis arched; tail whip-like 



Myliobatidae (page 427) 

 snout in two separate lobes; teeth molarial; tail whip-like, with a spine 

 prepelvic process median, rather short; pelvis greatly arched 



Rhinopteridae (page 443) 



MOBULOIDEI. 



Disk polygonal; pectorals broad, angular; copula imperfect; no produced rostral 

 cartilage 

 snout very broad, with two lateral lobes; teeth minute; tail whip-like 

 prepelvic process median, elongate; pelvis greatly arched 



Mobulidae (page 448) 



