344 LOWER VERTEBRATES. 



bone unossified above, so that it forms only a half-ring instead of a ring. This is the 

 genus JRanula. Three species are found on the Amazon, and a very elegant one, the 

 li. chrysoprasina, occurs in Costa Rica, see plate cit. Ranidae, Fig. 3. 



A remarkable Asiatic genus is Oxyglossus, which has the tongue angulate behind. 

 In nearly all other Ranidse the tongue has two processes separated by a deep notch 

 behind. 



The gradation in the ossification of the skull is not so great as in some of the other 

 families of Anura. Thus no genus has a frontoparietal fontanelle, and the ossification 

 does not extend so far on the other hand as to overarch the temporal fossa and muscle. 

 The range is seen first in the completion of the ethmoid bone above, and then in the 

 extension of the prefrontal bones towards each other on the middle line, (see pp. 272, 

 273, Ranidse, Figs. 3-\ 3, 3^^, 3=). At the end of the series is the restricted genus 

 Polypedates, where the ossification involves the derm of the skull, as in Trachycepha- 

 lus of the Hylidae, and Calyptocephalus of the Cystignathidse (see pp. cit. Fig. 5). 

 The species of Rana with completed nasal bones (pp. cit. Fig. 3'), and the genus 

 Polypedates, inhabit India. 



Edwaed D. Cope. 



