336 



L WER VER TEBRA TES. 



exceptional in having a longitudinal row of teeth on the roof of the mouth, on the 

 parasphenoid bone. Most of the largest species of this series belong to the genus 

 Hypsiboas. This is characterized by the presence of a thumb, in which the last 

 phalanges are co-ossified into a curved spine of dense translucent bone, with a very- 

 sharp apex. This is concealed in a sheath of skin, but readily penetrates an object 

 against which it is pressed. This is another arrangement for enabling the male to 

 maintain his hold on the female during the season of breeding. 



In the genus Phyllomedusa, the middle toes of both feet are reduced in size exactly 

 as in some genera of African lemurs (Arctocebus, etc.), so that the external toes oppose 



Fig. 200. — Xototrenia marsnpiatiat 



each other. This is an adaptation to the habit of seizing a limb round it, a mode of 

 securing a hold different from that which prevails in the family generally, where the 

 toes are attached to flat surfaces by adhesion of their terminal discs. Accordingly 

 the discs are small in Phyllomedusa. This genus is connected with the central 

 form Ilijla by intermediate forms, especially by the genus Agahjchnis. Of the 

 ninety-five species of the genus Myla, the largest are the U. dolicho2ysis of Xew 

 Guinea, and the IT. vasta of the "West India island of San Domingo. The head 

 and body are five inches long in both. They are exceeded in dimensions by the 

 Phyllornedusa hicolor, which occasionally reaches seven inches. The smallest Jlyla is 

 the H. pickeringii. which is an inch and loss in length. The common Hyla of the 



