MEXICAN TAILLESS AMPHIBIANS 131 



KEY TO GENERA OF MEXICAN HTLIDAE 



1, Derm of head of adults completely involved in cranial ossifi- 

 cation, forming a bony casque 2 



Derm of head of adults not involved in cranial ossification and 

 not forming a bony casque; head covered with soft loose skin; 

 no parasphenoid teeth 5 



2.^Posterior edge of bony casque studded with high, conical, erect, 

 bony spines; top of head bony; canthus rostralis sharply 

 defined, granular; snout rounded; loreal region concave; 

 upper labial borders smooth, not projecting conspicuously 

 beyond lower jaws; supratympanic ridge strongly elevated, 

 tubercular; supraciliary crest tubercular; interorbital space 

 concave; vomerine teeth in two nearly transverse rows on level 

 with posterior margins of choanae; no parasphenoid teeth; 

 tongue subcircular, not or slightly notched behind; pupil hor- 

 izontal, circular when contracted; tympanum circular, two- 

 thirds diameter of eye; fingers free; toes one-third webbed; 

 adhesive disks of fingers and toes smaller than tympanum; 

 tarsal fold distinct; large internal metatarsal tubercle; no 

 outer metatarsal tubercle; female with dorsal pouch. -.Qastrotheca (p. 133) 

 Posterior edge of bony casque more or less upturned, but without 

 high conical spines; upper labial borders projecting conspic- 

 uously beyond lower jaws; snout extended beyond symphysis 

 of lower jaws; females without dorsal pouch 3 



3. Inner metatarsal tubercle greatly enlarged and compressed; 



outer metatarsal tubercle quite small; eye separated from 

 outer margin of flaring labial border of upper jaw by an interval 

 equivalent to more than one-third of its diameter; posterior 

 edge of rugose bony casque not upturned; canthus rostralis 

 raised, curved, separating external nares; snout rounded; 

 loreal region very wide, concave; upper labial borders pro- 

 jecting and slightly upturned; interorbital space broader than 

 upper eyelid, deeply concave; vomerine teeth in two groups 

 between choanae; no parasphenoid teeth; tongue circular, 

 notched behind; pupil transversely oval; tympanum oval, 

 one-half to two- thirds diameter of eye; fingers slender, free 

 or with vestigial web at base; no projecting rudiment of poUex; 

 toes slender, one-third webbed; adhesive disks of fingers and 

 toes quite small, considerably smaller than tympanum; sub- 

 articular tubercles small, prominent; tarsal fold absent or 

 faint; skin of back closely granulated; underparts and inferior 

 surface of thighs coarsely granulated; upperparts brov/nish, 

 with large elongate insuliform or anastomosing dark-brown 

 black-edged spots; thighs sulphur yellow, marbled with dark 

 brown; upper surfaces of fore and hind limbs with large dark 



brown transverse spots; underparts white Pternohyla (p. 135) 



Inner metatarsal tubercle not greatly enlarged; eye almost in 

 contact with outer margin of flaring labial border of upper 

 jaw; tympanum distinct; transverse vomerine and longitudinal 

 parasphenoid teeth present, the former in two small clusters 

 and the latter in a single narrow row 4 



4. Palatine teeth present, forming slightly curved row on each side 



posterior to choanae; vomerine teeth in two narrowly separated 

 clusters between choanae; parasphenoid toeth small, closelv 



