mouth. The mouth is wholly unlike the adult mouth. It has usually a 

 disc called a labium (with upper and lower labia). Usually about the 

 edge of the labium are tubercles or papillae. At the inner edge of each 

 labium or at the very portal of the mouth opening itself are horny 

 crescents called upper and lower mandibles. On the upper and lower 

 labia are horny ridges of teeth or combs for scraping food. The tail has 

 two parts: the axis consists of muscle segments; and the fin consists of 

 upper and lower crests. 



The narrow-mouthed toad tadpole has no mouth disk, no labial 

 teeth, no papillae, no horny beak. The spiracle is next to the vent. 

 The eyes are on a lateral ridge. These tadpoles are small black 

 flattened creatures with some white on the tail axis or body. 



The ribbed toad {Ascaphus) has a mouth disk, an upper mandible 

 only, papillae on the lower lip or labium, upper labial teeth at least 

 two rows to a ridge, labial tooth ridges two to three above and seven 

 to ten below, a spiracle in the middle of the venter nearer the hind 

 legs than the snout, eyes straight back of and close to nostrils, dorsal, 

 equidistant from mid-dorsal line and lateral outline when viewed 

 from above. The tail is spathulate and rounded as in some mountain 

 stream tadpoles. The tadpoles are black or brown. 



The spadefoots have the vent in the middle position, the spiracle 

 below the body axis and on the left side, the papillae completely 

 around the labium except for a small interval above (absent in one 

 species), the papillary border not emarginate on the side, labial teeth 

 three to six ridges above and four to six ridges below, eyes dorsal 

 nearer mid-dorsal line than lateral outline, muscle segments of the 

 tail plainly visible. 



The toads usually have small blackish tadpoles with anus median, 

 papillae confined to the sides of the labium, upper and lower edges of 

 the labium toothed, sides of labium emarginate, labial teeth two ridges 

 above and three ridges below, eyes dorsal slightly nearer the lateral out- 

 line than mid-dorsal line. The spiracle is on the left side and is small. 



The frogs have medium to large tadpoles, with spiracle on the left 

 side, vent on right side of lower tail fin's base. The spiracle is near the 

 body axis; the papillary border is emarginate on the side; the labial 

 teeth are two or three ridges or more above and three or four or more 

 below. Some may have spathulate tails, if high mountain forms, 

 others may have upper tail crest high and far on to the body like a 

 tree frog tadpole, but most have the tail crests neither very high nor 

 extending far on the body. 



The treefrogs have small or medium tadpoles often with high 

 dorsal tail crest extending far on the body, the vent on right side of 

 ventral tail crest, and the spiracle on left side near the body axis. 

 Labial teeth two ridges above and two or three below. 



IO 



