‘874 The American Naturalist. [October, 
1. The sr Sener can not endure cooler climates (climatic bar- 
riers). 
2. They are true fresh-water animals (oceans and tracts-of 
‘land without water form topographic barriers). 
3. Being animals of ‘an ancient type, they are Seubably re- 
stricted by the occurrence of other fresh-water animals (brono- 
mic barriers). 
4. The faculties of distribation aré very limited. 
The Atyide are, therefore, confined to the fresh-waters of 
the tropics and subtropics; the distribution of the genera and 
species, especially of the more primitive ones, shows a remark- 
able character of survival. Only Caridina and Atya are of a 
‘more recent character, extending over continuous areas within 
the tropics. Because of the antiquity of the family it has no 
‘relations maong the recént forms of the littoral regions of the 
— tropical seas.” 
The AEE EN TEN can be drawnfrom thedistribution 
of the Atyidæ. The distribution of Cardinia shows that there 
must have existed a land connection between Africa, the Mas- 
caren Islands, the Seychelles, Persia, Ceylon,the Sunda Islands, 
the Mollucas, Siam, the Loo Choo Islands, Japan and the Bo- 
nin Islands, and between the Mollucas and Australia. 
The distribution of Atya shows that this land area extended 
over the Philippine, Caroline, Fiji and Samoa Islands, and the 
presence of Atyoida bisulcata on the Society and Sandwich Is- 
lands, proves that this land extended also to these islands and 
probably also to the west coast of America (Atya scabra Mex- 
ico, Nicaragua Baur). The presence of Cardinia paredena 
‘Kingsley, in Lower California is another proof of this connec- 
tion. The presence of Atya scabra‘on the Cape Verde Islands, 
and of Atya gabonensis in Gaboon and the Orinoco, can only 
be explained by a former connection of neni rar America 
(Ortmann). 
Geographical Distribution of the Formicidæ of the Pacific Ocean. 
The Formicidæ are a very old: group. Their first remains 
have been found in the lowest Jurassic : Palæomyrmex prodro- 
mus Heer,” Lower Lias of. Schamblen, Canton pan Swit- 
* Heer O, Die Urwelt der Schweiz. Zürich., 1865, p. 9I-~ : 
