THE PHILIPPINE ISLANDS 
45 
mixed type — partly Philippine, partly Indo-Malayan ; 
but there can be little doubt that they have formed, at 
a period more or less remote, the passage by which the 
Indo-Malayan mollusca have entered the archipelago to 
mingle with the indigenous genera. Thus we find the 
great Nanince and Cyclophori of the Sunda Islands largely 
represented, as well as Amphidromus , Kcdiella , and others, 
all of which are represented in Java, Sumatra, and 
Borneo, as well as in India or Indo-China, but scarcely 
at all, or in greatly diminished numbers, in the islands 
farther east. 
The Polynesian and eastern connection is exemplified 
by the occurrence of T'ornatellina , Eudodonta , numerous 
species of Helidna and Leptopoma, and a considerable 
number of Pupina and Diplommatina. About fifteen 
species of land shells are common to the Philippines and 
Amboina, and some writers have considered it probable 
that a land connection existed at one time with the 
countries to the east and south, but in this opinion Mr. 
Cooke does not share. 
Prom the foregoing it will be seen that the zoology of 
the group is of unusual interest, presenting problems in 
geographical distribution which have as yet not been 
satisfactorily explained. Taking all the facts yet known, 
we find a wonderful amount of peculiarity throughout, 
great luxuriance of development in some of the lower 
groups, and many deficiencies in the higher, especially in 
the mammalia. This luxuriance and peculiarity, com¬ 
bined with poverty in the forms of life, implies great 
antiquity and long - continued isolation from adjacent 
countries. The presence of a tolerable variety of mam¬ 
malia, closely allied to those of other Malayan countries, 
shows that the time from which the isolation dates is 
not very remote geologically; but it is less easy to 
