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 then- digits {Dcndro- 

 bate^, 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 dc 

 not overlap. The lungs are 

 complex with restricted free 

 lumen. The first spinal nerve 

 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, iUa 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. 



Fig. 175.— Xencypus {Dactylethra) laevit. 



