Teeth are almost entirely absent, except in _Notaden_, which has teeth on the vomers. The omosternum is mostly absent, except in _Engystomops_ and in some species of _Bufo_, while in _Notaden_ it is merely vestigial. The metasternum shows more variety. The tympanum is usually distinct, but varies even within the same genus, being hidden beneath the skin or being entirely absent. The terminal phalanges are modified according to the habits of the species, but they are never claw-shaped. The Bufonidae are connected in various directions. The Neotropical _Engystomops_ greatly resembles the likewise Neotropical Cystignathoid _Paludicola_, and the Australian _Pseudophryne_ closely approaches the Australian Cystignathoid _Crinia_. It is therefore all the more remarkable that a similar approach, in another direction, namely, towards the Firmisternal family of the {167}Engystomatidae, is indicated by the Mexican _Rhinophrys_ and the Australian _Myobatrachus_. However, since there are no true Engystomatidae in Australia, although several genera occur in Papuasia, these cases may be instances of convergence without necessarily implying relationship. An unmistakable line of connexion leads, according to Boulenger, to the Pelobatidae, the link being the Himalayan _Cophophryne_, with very strongly dilated sacral diapophyses, with a single condylar articulation of the coccyx with the sacral vertebra (as in some Indo-Malayan Pelobatidae), while this articulation is bicondylar in all the other Bufonidae. [Illustration: FIG. 34.–Map showing distribution of Bufonidae. The vertical lines indicate the occurrence of Bufonidae, but not of _Bufo_.] The whole family is divided into nine genera with more than a hundred species, of which only about fifteen do not belong to the genus _Bufo_. The distribution of the family is well-nigh cosmopolitan, with the remarkable exception of Madagascar, Papuasia, and the small islands of the Pacific; _Bufo_ has been wrongly said to inhabit the Sandwich Islands. The greatest number of species, chiefly _Bufo_, occur in the Neotropical region, the greatest number of genera in Central America, where _Bufo_ is rare, and in Australia, where it is absent. A. Pupils contracted to a horizontal slit. Typically arciferous. _a._ Australian. Tympanum invisible. Fingers and toes not dilated. 1. With vomerine teeth. Both the omo- and meta-sternum are rudimentary. East Australia: .......... _Notaden bennetti_. 2. Without vomerine teeth. Omosternum absent. Metasternum cartilaginous: .......... _Pseudophryne_, p. 168. {168}_b._ Not Australian. 1. Omosternum narrow and cartilaginous. Metasternum with a bony style ending in a cartilaginous disc. Fingers and toes slightly swollen. Neotropical: .......... _Engystomops_, p. 168. 2. Omosternum absent. Metasternum cartilaginous.