1897.] The Origin of the Galapagos Islands. 873 
cies of which might be regarded as a fourth form of Xipho- 
caris, lives in the subterranean waters of Carinola, a perfectly - 
isolated locality in no way connected with the others named. 
The third primitive genus, Atyaéphyra, is found near the 
locality of Troglocaris on the northern borders of the Medit- 
erranean Sea. The scattered localities at which are found the 
species of these three genera forming the subfamily Xipho- 
carine are no doubt the remains of a more universal distribu- 
tion in former times; the species now living show the charac- 
ter of true survivals.” 
“In the subfamily Atyine, the genus Atyoida shows a sur- 
vival character similar to that of the Xiphocarine, being 
recorded from the Sandwich Islands, Tahiti and Southern 
Brazil.” 
“ The genus Caridina appears to be nearly a circumtropical 
one. Its range is divided into two very unequal parts; the 
one comprising the West Indies [and California] and contain- 
ing only one [two] species, the other comprising a continuous 
area of the Old World and containing at least nineteen other 
species. This area extends from South Africa along the east 
coast to the southern borders of the Mediterranean Sea and to 
Persia, crossing the islands of the Indian Ocean and Indo- 
Malaysia to Japan and Australia. It is very probable that 
further investigations will prove that the range of Caridina is 
a somewhat different one, since fresh-water crustacea of smaller 
size are mostly neglected by collectors, and the fauna of the 
fresh-waters of most tropical countries are very little known.” 
“The distribution of the most extreme genus of the family 
Atya is somewhat similar to that of Caridina. Itis found, 
like the latter, in the West Indies and Indo-Malaysia, but there 
are some modifications. One species is known from West 
Africa, which is identical with another described from the 
Orinoco, and there is recorded one species from the Cape 
Verde Islands, identical with the common West Indian form.” 
“The other range of the genus Atya extends over the islands 
of the Pacific from Sumatra to the Samoan Islands” [and 
western Central America]. 
“The conditions of geographical distribution of the Atyidee 
are as follows :— 
