4o6 
ZOOLOGY OF THE FAR FAST. 
Fresh water. 
Tachaea chine nsis, Thiel. 
Ogura Pond, near Kyoto. 
Ichthvoxeniis japonensis, Richardson. 
Fake Biwa. 
Among the Mysidacea Siriella watasei, Gastrosaccus vulgaris and Anisomysis 
ijimai are so far only known from the seas in the neighbourhood of Japan, while 
Rhopalophthalmus egrcgiiis has a wide distribution in the tropical and sub-tropical 
parts of the Indian and Pacific Oceans from India to Japan. 
On the other hand the brackish water species, Neomysis awatschensis, is an 
immigrant from the North, known hitherto from Kamtschatka. 
The two Isopods, Tachaea chinensis and Icllthyoxenus japonensis, are representa- 
tives of genera widely distributed in fresh and brackish water in India, Indo-Malaysia 
and the islands of the East Indies. 
From China the following species were obtained, all from fresh water : — • 
Tai-Hu. 
Tachaea chinensis, Thiel. 
Exosphaeroma oregonensis, Dana. 
Whangpoo River, bei,ow Shanghai. 
Neomysis nigra, Nak. 
Cleantis annandalei , Tattersall. 
Exosphaeroma oregonensis, Dana. 
Exosphaeroma chinensis, Tattersall. 
Of these species, Tachaea chinensis is common to Japan and China and is a 
representative of a southern and tropical fauna. The other species have probably 
entered the brackish waters of China from the North and are evidence of a northern 
element in the fauna. Neomysis nigra is known from Japan and is very closely 
allied to the northern A^. awatschensis. E. oregonensis is known from brackish water 
in Alaska and from several places along the western shores of N. America to as far 
South as California. The brackish water species of these groups of Crustacea found 
in China and Japan appear to suggest therefore at least two distinct sources of origin 
for that fauna. 
The Mysids, Neomysis awatschensis and N. nigra, are distinctly immigrants from 
the North and there is no suggestion of a southern element in the Mysidacean fauna 
of the brackish waters of Japan and China. Both species are of the nature of relict 
species. 
Among the Isopods of the same fauna Tachaea chinensis found in both China 
and Japan is of southern origin, \yhile the two species of Exosphaeroma and Cleantis 
annandalei probably entered from the North. The purely freshwater species Asellus 
aquaticus and Caecidothea kawamurai are survivors of a fauna of much earlier times, 
when Japan was in land connection with both America and the rest of Asia. 
