POTAMOTRYGON LATICEPS. 117 



mouth waved, small, width two fifths Length of snoul 



curved forward; teeth equal . . rirculnris (page 419) 

 Disk longer than wide 



tail longer than disk, tuberculate on top and sides 



mouth medium, width two thirds of distance from end of snout 



waved, teeth nearly equal . . . humerosus 'page 419) 

 mouth small, width two fifths of distance from end of snout 

 curved; teeth small, flattened, inward angle sharp 



spotted with light, and with dark . signatus (page 420) 

 mouth small; tail with median row of tubercles 



reticulate with brown; spots yellow magdalenae (page 421) 

 mouth small, curved, with two papillae 

 tail with median and lateral tubercles 



spotted with scattered spots of light on brown 



hystrix (page 422) 

 mouth small, curved, with five papillae 

 tail with median and lateral tubercles 



spotted with yellow . . . motoro (page 423) 



Disk circular 



tail more than twice length of disk . . . orbicularis (page 423) 

 Disk broader than long 



tail shorter than body, median tubercles on base 



a net-work of blackish streaks . . . brachyurus (page 424) 

 tail much longer than disk, with median tubercles 



a net-work of hexagonal meshes . . . reticulatus (page 424) 



POTAMOTRYGON LATICEPS, Sp. llOV. 

 Plate 31, fig. 3-4; Plate 55, fig. 6 (vertebrae). 



Disk subround, little longer than wide, slightly narrowed posteriorly. 

 Mouth moderate, in width half its distance from the end of the snout, with 

 rather abrupt curves in the upper jaws on which some of the teeth are larger. 

 with five papillae, and a sixth behind the median papilla. Teeth black, rather 

 smooth, convex, of various sizes, in fi rows. Eyes small, distance apart one 

 and one half times their distance from the end of the snout. Spiracles larger 

 than the eyes, interspiracular width about equal distance from eyes to end of 

 snout. Head broad, crown convex. Ventrals broad, angles rounded. Base 



