34 
Annals of the Tkansvaal Museum. 
therefore favour the supposition I have made for an extension in a north- 
easterly direction of the distribution area of Heleophryne. Lastly, in the 
arboreal habit of this frog we have another possible clue to the problem, 
for granting that in Upper Cretaceous times the direct connection between 
South Africa and Australia had largely disappeared, yet stepping-stones 
in the form of a chain of sinking islands affording opportunity for the 
dispersal of some arboreal creatures only, may still have existed. 
Ranidae. 
The whole family of Ranidae is distributed as follows: — Ceratobatrachus, 
which has teeth in both jaws, is known only from the Solomon Islands: 
the Raninae, which have teeth only in the upper jaw, belong almost entirelv 
to Arctogaea, and except for the genus Rana, which ranges throughout the 
whole region, are limited mainly to tropical and sub- tropical areas : the 
Dendrobatinae, which are characterized by an entire absence of teeth, occur 
in Madagascar, Gabun, and the neotropical region. 
The genera of Raninae (Ranidae of many authors) fall into two sections 
according to the presence or absence of supernumerary digital phalanges, 
the former section comprising the following genera : — Chiromantis, Cassina, 
and Hylambates, which belong to tropical and South Africa, Rothschildia 
of Abyssinia, Rappia and Megalixalus occurring in tropical and South 
Africa and Madagascar, with an odd species of the latter genus in 
the Seychelles, Rhacophorus of Madagascar, India, Malaya, and Japan, 
Mantidactylus of Madagascar, Ixalus of India and Malaya, Nyctixalus 
of East Indies, Phrynoderma of Burmah, and Chirixalus of the 
Karin Hills. Dr. Gadow says it is doubtful if all these genera are 
thereby more nearly related to each other than to the rest of the Raninae ”, 
but as the African members — with the possible exception of Chiromantis — 
seem to be more closely related to each other than to Rana, and as the 
distribution of the whole section is very suggestive of a former continuity 
through the Indo-Oceanic continent, I am regarding them as a natural 
group, and, as will be explained later, I suspect that this is the older section 
of the family. The other section of the Ranidae, comprising genera which 
are without supernumerary digital phalanges, occurs throughout Arctogaea 
and the tropics of both worlds, and has the following genera in South 
Africa : — Rana, Arthroleptis, and Phrynobatrachus, in addition to which 
there are one or two monotypic genera in tropical Africa, for instance, 
Phrynopsis of Mozambique : these genera, with the exception of Rana 
with its fifteen species in South Africa out of a total of about 150 species 
which range throughout the whole tropical and temperate Arctogaea hardly 
penetrating into Notogaea, and Arthroleptis which has an odd species in 
Nossi Be (with a generic ally in th3 Seychelles) are peculiar to the 
African continent : on the other hand, Madagascar has no peculiar 
gequs belonging to this section, and indeed its only representatives 
are two species of Rana — one of them being the R. mascariensis, 
widely distributed in tropical and South Africa — and the single species 
of Arthroleptis, which, however, appears to be confined to Nossi Be. 
It is poss ble therefore that the Madagascar representatives of this 
section are merely straggling immigrants of quite recent date, and we 
can be sure that this island was outside the area of evolution of the 
