GENERA OF THE ARCIFEROUS ANURA. 69 



The seven natural families are characterized as follows : 



I. Sacral diapophyses dilated ; vertebrjB opisthocoelian. 

 Ribs ; xiphisternum of two divergent limbs ; usually fronto-parietal 



fontanelle and coccygeal diapophyses ; outer metatarsi separated 



by web, . '. Discoglossidse. 



No ribs or coccygeal diapophyses ; usually complete frontoparietals, 

 and single coccygeal condyle : xiphisternum an osseous style ; ex- 

 ternal metatarsi bound, Asterophrydid^. 



II. Sacral diapophyses dilated ; vertebrae procoelian. 

 Terminal phalanges simple conic continuous; coccyx united by 



condyles, PelodytidiB. 



Terminal phalanges continuous conic; coccyx connate with 



sacrum, Scaphiopodidas, 



Terminal' phalange with a swollen base and slender curved claw- 

 like termination, articulated beneath the penultimate; coccyx 

 united by condyles, Hyhdaj. 



III. Sacral diapophyses cyliudric ; vertebras procoelian. 



Mandible bearing teeth, HemiphractidiB. 



Mandible edentulous; external metacarpals usually bound to- 

 gether, rarely free, CystignathidjB. 



The only family features as above given, which seem to have a functional signifi- 

 cance, are the structure of the terminal phalanges as an adaptation to arboreal life 

 in the Hylida3, and the increase of raptorial power by the addition of another set 

 of teeth in the Hemiphractida^. Yet for the first mentioned function how many other 

 arrangements are employed among other genera ? 



We are at present acquainted with 265 species of this tribe, which represent 69 

 generic types : they represent the families in the following proportions and regions : 



Distribution. 



R. Palaearctica. 

 R. Paljeotropica, Australis. 

 R. Palseotropica ; Palaearctica. 

 R. Palaearctica, Nearctica. 

 (R, PaltBotropica) R. Palaearctica, 

 Nearctica, Neotropica, Australis. 

 R. Neotropica. 

 R. Neotropica ; Australis. 

 The generic forms are all peculiar to their zoological regions, except Hyla, found 

 wherever its family occurs, and Borboroca3tes, common to Australia and the southern 



portion of South America. 



18 



Discoglossidae, 



Gen. 

 . 5 



Sp. 



6, 



Asterophrydidse, 

 Pelodytida3, 

 Scaphiopodidae, 

 Hylida3, 



. 4 

 . 2 

 . 5 

 . 17 



5, 



2, 



9, 



132, 



Hemiphractidae, 

 Cystignathidae, 



. 1 



. 35 



2, 

 109, 



