258 THE PLAGIOSTOMIA. 



skull produced in a narrow pointed rostral cartilage that is rarely obsolete; 

 tail moderate to slender, commonly with two small, rayed dorsals and with a 

 more or less imperfect membranous caudal, without a serrated spine; copula 

 unsegmented; nasoral grooves; teeth small, in pavement; pelvis transverse, 

 with lateral prepelvic extensions: Raioidei (page 259) 



Pectorals and body broad, polygonal to rounded; skull not produced in a 

 rostral cartilage; tail slender whip-like, with a serrated spine and with or with- 

 out narrow membranous fins, or a rarely present rayed fin; copula segmented; 

 nasoral grooves ; teeth' small, in pavement ; a median prepelvic process or spine : 



Dasybatoidei (page 259) 



Pectorals and body in a broad polygonal disk; skull bearing cranial sections 

 of the fins, not produced in a median rostral cartilage; nasoral grooves; copula 

 imperfect; tail slender whip-like, with a serrated spine or rarely without; teeth 

 broad, molarial; pelvis arched forward, with a median prepelvic process: 



Myloidei (page 259) 



Pectorals and body broad massive angular; skull broad, preceded by lateral 

 sections of the fins, without a produced median rostral cartilage; tail slender, 

 whip-like; copula incomplete; teeth minute, in bands; pelvis arched forward, 

 with a median prepelvic process: .... Mohuloidei (page 259) 



Synopsis of Families. 



Rhinobatoidei. 



Disk small; rostrum produced, toothed on its edges; dorsals and caudal present 

 copula unsegmented; no electric battery; no nasoral grooves 

 pectorals not continued forward at the side of the head. 



Pristidae (page 260) 

 Disk moderate; rostrum more or less produced, not toothed on its edges; dorsals 

 and caudal present 

 copula unsegmented; no electric battery; no nasoral grooves 



pectorals continued at side of head, not reaching end of snout 



Rhinobatidae (page 266) 

 Disk large, broad, rounded; dorsals and caudal present 



copula unsegmented, nasoral grooves rudimentary or absent 

 pectorals continued to end of snout; rostral cartilage short 



Discobatidae (page 287) 



