AGLOSSA 



143 



rally look to the Engystomatidae as the connectiug liuk between 

 the Eanidae and the Arcifera, through Bufonoid creatures still 

 with teeth in both jaws. If, on the other hand, we take the 

 dilatation to be a further development from more or less 

 cylindrical processes, then the Eanidae can be considered as 

 having sprung from Cystignathoid creatures, which have con- 

 solidated their pectoral arch into the firmisternal condition ; 

 and in this case the Firmisternia would not be a natural 

 group, the Engystomatidae pointing, to the Bufonoid stock. 

 This would, to a great extent, mean a reversion to Cope's 

 idea. 



Sub-Order 1. Aglossa. — The two diagnostic peculiarities 

 of the few members of this group are : first, the absence of 

 a tongue ; secondly, the union of the Eustachian tubes into 

 one median pharyngeal opening in the posterior portion of 

 the palate. 



The pharyngeal opening and the tubes themselves are wide, 

 the tympanic cavities are present, but the tympanic discs are 

 not distinct from the 

 rest of the skin. " The 

 fronto-parietal bones are 

 fused into one mass, a 

 rare feature in the 

 Anura. The nasals are 

 large. Pipa and Hyme- 

 nochirics have no teeth, 

 Xeno2nis has teeth on 

 the upper jaw. The 

 vertebrae are opistho- 

 coelous and typically 

 epichordal in their de- 

 velopment ; the second, third, and fourth carry long ribs, which in 

 old specimens fuse with the supporting diapophyses. The sacral 

 diapophyses are enormously dilated, and the sacrum is fused with 

 the OS coccygeum. The serial number of the sacral vertebrae 

 exhibits a most interesting gradation. In Xenopus the ilium 

 is carried by the diapophyses of the 9th, in Pi2m the 9th and 

 8th, in Hymenochirus the 7th and 6th. In these cases the 

 two diapophyses of each side are fused together into a single 

 broad blade, and their original duplicity is indicated only by the 



XENOPUS. 



Fig. 28. — Map showing distribution of Aglossa. 

 Hymenochiruf; to be added in Equatorial Africa. 



