182 PROCEEDINGS OF THE ACADEMY OF 



presents less variety than in the other suborders. The o. o. coracoi'dea are 

 distally much dilated horizontally, especially anteriorly, and in close contact 

 on the median line ; their axis is transverse. The o. o. 'epicoracoi'dea are also 

 transverse, and usually in contact medially, always resting against the ante- 

 rior angles of the coracoi'dea. The manubrial and xiphisternal pieces are 

 dilated proximally and become cylindrical or styloid, terminating in a carti- 

 laginous disc. The only other cartilages of the sternum are the intersutural. 

 Frogs with this sternum always have a cylindrical diapaphyses of the sacrum, 

 and never a fronto-parietal fontanelle. In the ordinary type of sternum the 

 coracoi'dea are little or not dilated, and converge posteriorly without meeting, 

 while the epicoracoi'dea converge anteriorly and are connected with the for- 

 mer by longitudinal arched cartilages ; hence I have termed these Arciferi. 

 Among the toothless Batrachia or Bufoniformes (which have dilated sacral 

 diapophyses, except in one genus), some forms show an approach to the Rani- 

 form style, while in the Aglossa we find the most exaggerated Arciferous 

 type. 



The Raniformes embrace but one family, but this imitates well many 

 genera of Arciferi. The metropolis of the former, as of the Acrodonta, is the 

 Regio Palaeotropica, while the latter have but few representatives out of the 

 R. R. Neotropica and Australis, where but one or two species of the former 

 occur. In both we can trace a series in which the outer metatarsal is gradu- 

 ally liberated from the penultimate, to afford greater extension for the web 

 in the most aquatic types, and among those where these bones are bound, 

 from webless to webbed types. In both we have burrowing and arboreal 

 genera. 



In strict reference to the extension of the webs the following parallels may 

 be drawn : 



Raniformes. Arciferi. 



External metatarsal free. 



Aquatic. Rana. Pseudis. 



Subfossorial. Hoplobatrachus. Myxophye3. 



External metatarsal attached. 



Feet webbed. 



Burrowing. Pyxicephalus. Tomopterna. 



Arboreal. Leptopelis. Hyla. 



" Hyperolius. Hylella. 



Subarboreal. Hylambates. Nototrema. 



Feet not webbed. 

 Terrestrial. Cassina. Cystignathus. 



" spurred Hemimantis. Gomphobates. 



Comparing the genera in a general physiological sense, we may parallelize 

 further 



Aquatic, with digital dilatations, 



Heteroglossa. Acris. 



n i j i f Trachycephalus. 



Arboreal. Polypedates. | Hyla. 



Rhacophorus. Agalychnis. 



It is, however, remarkable that the Raniform tree-frogs nearly always have 

 the external metatarsal bone free, the Arciferous always bound ; the terminal 

 phalanges of the latter are constructed on a ball and claw type, in the former 

 they are T-shaped or bifurcate, except in the single West African genus Lep- 

 topelis, where the South American type is repeated. 



Evidently belonging to former times, as their present weak representation 

 and generalized structure seem to indicate, are two families of Arciferi not 



[Aug. 



