VI HYLIDAE 207 



only, much resemble each other in the curious shape of the liead, 

 which forms a flat projecting snout, used probably for digging in 

 rotten wood in search of insects. There is a peculiar degradation 

 in the extent of dentition of the palatal region. Biaghna and 

 Triprion are the only Anura which possess a longitudinal row of 

 parasphenoid teeth. Diaglena pctasata of jMexico and D. jordani 

 of Ecuador have, moreover, a transverse row of teeth on the 

 palatine bones in addition to those on the vomer. 



lYijjrion petasatus of Yucatan has i)arasphenoid and vomerine 

 teeth. The head is a bony casque, with strong superciliary 

 ridges, the skin being extensively ossified. The mouth forms 

 a flat snout, owing to the long projection of the upper over 

 the lower jaw. The skin of the back is smooth brown with 

 darker spots ; the under parts are uniform whitish. The male 

 has a subgular vocal sac. Like Diaglena and CorytJwmantis they 

 possess adhesive discs on the fingers and toes, and climb trees. 

 The total length of this curious creature is 2 inches. 



Corythomantis greeningi of Brazil has a similar head. The 

 vomers alone carry teeth, besides of course the maxillae. Tlie 

 pupil is rhomboid. The tongue, as in the 

 two previous genera, is joundish, scarcely 

 free. General colour above olive, with 

 darker freckles ; the sides are studded with 

 whitish tubercles ; the under parts are 

 whitish. The male is devoid of vocal sacs. ^ ,, tt , .- ^ 



Fig. 41. — Head ot Corytho- 

 Total length 3 inches. mantis greeningi. x ]. 



Pternohyla fodiens of Mexico ap- ^BUZchT'^^''"^'' '"'' 

 proaches the previous three genera by the 



curious shape of the head and prominent upper jaw, although 

 these features are not so exaggerated. The dentition agrees 

 with that of Corythomantis and other normal tree-frogs. The 

 fingers and toes are not provided with discs, in conformity with 

 the burrowing, not climbing, habits of this creature. The 

 next following three genera connect the Hylidae with the 

 Cystignathidae. The sacral vertebrae are but slightly dilated. 



Acris. — The adhesive discs are very small, the tympanum is 

 indistinct. A. gryllns, the only species, inhabits the greater part 

 of Eastern and Central North America, extending northwards 

 into Canada. It attains a length of 1-^ inch. The colora- 

 tion is very changeable, in adaptation to the surroundings. As 



