ANURA. 309 



which especially love dark and damp hiding places ; others live 

 indifferently on land or in water. In the first case the five toes 

 of the hind feet are entirely without a connecting membrane, 

 or they have an incomplete one ; exceptionally however they 

 are completely webbed (Pelobates). In the second case, on the 

 contrary, the hind feet are, as a rule, completely webbed. The 

 land-frogs usually seek the water only at spawning time ; they 

 crawl, run and hop on the land, or dig passages and holes in the 

 earth (Pelobates, Alytes), or they are able to climb up shrubs 

 and trees by means of discs on the ends of their digits (Dendro- 

 bates, Hyla}. About 900 species are known. 



Sub-order 1. AGLOSSA. There is no tongue and the eus- 

 tachian tubes are united to 



open by a median opening 



into the pharynx. The tym- 

 panic membrane is not 



distinct from the rest of the 



skin. The vertebrae are opis- 



thocoelous and the 2nd, 3rd 



and 4th carry ribs which tend 



to fuse with the transverse 



processes. The transverse 



processes of the sacrum are 



dilated and confluent with the 



urostyle. The epicoracoids do 



not overlap. The lungs are 



complex with restricted free 



lumen. The first spinal nerve 



FIG. 175. Zenopus (Dactylethra) laems. 



is present. They are entirely 



aquatic in habit. The tadpoles of Xenopus have a pair of spira- 

 cles (branchial openings), and according to Bles have the normal 

 form but they are without " internal " gills or horny jaws. They 

 feed on micro-organisms and use the gill slits simply for 

 filtering. They possess a sucker, and the external gills are 

 present in the just-hatched form, but soon disappear, the 

 larval respiration being entirely by lungs. 



Fam. 1. Aglossidae with the characters of the suborder. Xenopus 

 Wagl. (Dactylethra], upper jaw toothed, ilia to 9th vertebra, pupil round, 

 phalanges pointed, fingers free, toes broadly webbed and the first three 

 have horny nails, trop. and S. Africa : X. laevis the clawed-toad, plathander. 



