VI 



IIVLIDAK 20; 



of thill ;ui(l sliglitly elevated ridge or fold of the skin extends on 

 to the neck. The suggestion, th.it this seam is burst open, in 

 order to set the full-grown young free, instead of tlieir passing 

 through the existing opening, is scarcely credible. 



These Neotropical tree-frogs seem to be rare, and females with 

 embryos are of course still more uncommon, so that the best 

 account of their structure is still that given by Weinland ^ of K 

 ovifeniDi. How the eggs get into the pouch has not yet been 

 observed, but it is most likely with the help of the male, im- 

 mediately after fertilisation. The pouch forms two blind sacs 

 which extend forwards over the sides of the back. 1'he eggs are 

 large, 1 cm. in diameter, and the enclosed embryos, or rather 

 tadpoles, had a length of 15 mm., with a large amount of yolk still 

 contained in the spirally wound intestine. The first two gill-arches 

 carried each a double thread, wdiich expanded into a funnel- 

 shaped membrane, not unlike the Hower of a Convolvulus, and 

 furnished with a capillary network ; the stalk contained muscular 

 fibres. Tliese most peculiar structures are of course the much 

 modified external Q-iUs, Those of N. testudineum and N. cornutum 

 are likewise bell-shaped. 



Hyhlla differs from Hyla chiefly by the absence of vomerine 

 teeth, and consists of about half-a-dozen small species, about one 

 inch in lengtli. The fact tliat two species live in Queensland 

 and Xew Guinea, while the others are natives of tropical America, 

 suffcrests that this a;enus is not a natural but an artificial 

 assembly, an instance of convergent evolution. 



rityllo medusa, composed of about one dozen species of tree-frogs, 

 is characterised by the vertically contracted pupil, large adhesive 

 discs, and the opposable nature of the inner finger and of the 

 hallux, tlie last joints of which are like thumbs. The sacral 

 diapophyses are strongly dilated. The range of the genus 

 extends from tropical Central America to Buenos Aires. Most 

 of the species are about 2 inches in length, blue -green to 

 violet above, with white purple-edged patches on the sides of the 

 body; the under parts uniform white, or with purple or l)rown 

 patches. The , male has a subgular vocal sac. Some have more 

 or less distinct parotoid glands. Ph. dacnicolor of ]\Iexico is 

 uuituriu green above, whitish below, and attains a size of more 

 than ;'. inches. In FJi. liicohir of Brazil, the skin of the upper 



' Arch. AniiJ. tindPhys. 1854, p. -149. Also Boulenger, P.Z.S. 1898, l>. 107. 



