CYSTIGNATHINAE 221 



in a frothy mass floating upon the surface of the water. The 

 eggs measure only 1 mm. and are without pigment, and with ex- 

 tremely little yolk. The larvae become free-swimming within from 

 eighteen to twenty-four hours after the first segmentation. When 

 ready for hatching they wriggle their way through the froth to 

 the water below, and hang into it from the floating froth. 



P. biligonigera s. notata, in Brazil, lacks the lumbar gland, the 

 place of which is marked by a black spot. The upper, parts are 

 olive, with darker marblings and a dark lateral stripe. The male 

 has a black throat and two external vocal sacs. Hensel found 

 the eggs, in Eio Grande do Sul, in September, forming a frothy 

 mass of the size of a fist, floating between grass upon the water 

 near the margin. 



The following three genera may serve as Australian examples, 

 especially since we are indebted to Baldwin Spencer for interesting 

 observations made on their habits in Central Australia. 1 



Chiroleptes, of which six species are known, is easily recog- 

 nised by the first finger, which is opposed to the others. The 

 sacral diapophyses are slightly dilated. The general shape is that 

 of a thick-headed, rather stout land-frog or of a tree-frog. The 

 tympanum is distinct, and the toes are only half webbed, or even 

 less, except in Ch. platycephalus, in which the toes are entirely 

 webbed and the tympanum is indistinct. This species is about 

 2 inches long, uniformly olive-green above, with a few tubercles 

 on the otherwise smooth skin. Other species rather resemble the 

 European Natterjack in coloration. 



Spencer's account is as follows : " In Central Australia Ch. 

 platycephalus seems to prefer the hard clay pans rather than 

 sandy creeks, as the sand-beds of the latter are too loose for the 

 formation of the burrow. We came across the animal first when 

 encamped by the side of a very shallow clay pan, the floor of 

 which was deeply cracked with the sun's heat. Around the edge 

 were withered shrubs of Chenopodium nitrariaceum, and it was at 

 the base of these that the black fellows looked for the burrow. 

 In the hard-baked clay were imprints made by the frog as it 

 burrowed, and about a foot underground we came across the 

 animal, puffed out into a spherical shape, and just filling up a 

 cavity, the walls of which were moist but not wet. The ground 



1 Report on the Work of the Horn Scientific Expedition to Central Australia, 

 pt. ii. "Zoology," 1896, p. 164. 



