PLATE 31. 



POTAMOTRYGONIDAE. 



Fig. 1-2. PoTAMOTRYGON ciRCULARis (Page 419). Fig. 3-4. Potamotryqon laticeps (Page 

 417). 



1. Dorsal view. Disk 15^ inches long. M. C. Z. 291. 



2. Mouth and nostrils. 



3. Dorsal view. Disk 16 inches long. M. C. Z. 605. 



4. Mouth and nostrils. 



i 



