38 
Annals of the Transvaal Museum. 
however, extensive land connections stretched between North and South 
America, and the Greater Antilles were united with Mexico and Central 
America : but at the end of the Miocene the geographical relations of that 
part of the world were much the same as to-day, and no profound changes 
have occurred since. It follows therefore that some very important 
deductions can be made by comparison of the Mexican fauna with that 
of the Antilles. The facts are : — 
Cystignathidae, extending from their South American centre into 
Mexico and the Antilles, but not occurring in the United States. 
Hylidae, well represented in South America, Mexico, and Antilles, 
and extending throughout North America. 
Bufonidae : Central America and Mexico are one of the centres of 
this family, and it extends into the Antilles. 
Engystomatidae, well represented in South America, occurring in 
Mexico, a few in North America, but none in the Antilles. 
Ranidae : a number of peculiar genera in the north-west portion 
of South America, but in Mexico and North America only the genus Rana 
occurs and there are none in the Antilles. 
Pelobatidae, extending from North America into Mexico, but not _ 
reaching Central America nor the Antilles. 
Apoda : they occur in South America and in Mexico, but are not 
known from the Antilles. 
From consideration of the Ranidae and Engystomatidae it will be 
seen that the transatlantic bridge could not have included the Greater 
Antilles, and in fact it must have been appreciably south of that region. 
And if we suppose that the transatlantic connection as a complete bridge 
came to an end at an earlier date than the Antillean land connection, at 
the same time making due allowance for the great length of the former, 
it can easily be shown that all these facts of distribution are in accordance 
with the speculations made in this paper concerning the place of origin 
and the migrations of the various Anura families. The absence of the 
Ranidae and Engystomatidae from the Antilles is quite comprehensible 
when we regard them as old-world families which crossed over to the 
neotropical region at a time when the land- bridge was just beginning to 
give way, and when eventually they had travelled northwards as far as the 
Antillean bridge this was no longer complete. That Bufonidae, Hylidae, 
and Cystignathidae occur in the Antilles is what we should expect of groups 
which are American in origin, but whereas the Bufonidae have been able 
to avail themselves of the transatlantic bridge, this is not the case with 
the other two families : the explanation no doubt lies in the fact that the 
Cystignathidae and probably also the ITylidae had their centre of origin 
far south, perhaps in the great land area lying between Australasia and 
South America, and by the time they had advanced northwards into the 
transatlantic bridge, this had begun to break up, whereas in the case of the 
Bufonidae the American terminus of that bridge was probably nearer their 
centre of origin. 
The various tertiary land connections of the Ethiopian region as 
indicated in this paper do not furnish a complete explanation of all the 
distribution data: it is difficult to understand, for instance, why such 
