460 Tourn. of the Asiat. Soc. of Bengal. [Nov. & Dec., 1915. 
if we turn our attention from these so-called species to the 
larger groups they represent. There is no doubt, if we accept 
Simpson’s classification (which appears to be the most complete 
to the section or subgenus Lymnium, Oken. They represent, 
moreover, two groups in that section, the majority belonging to 
what Simpson calls the ‘‘Group of Unio pictorium,’’ while 
U.galilaei, U.rothi and U.simonis belong to his ‘ Group 
of U. litioralis.’’ 
ow Unio as a genus is mainly but not exclusively 
Holarctic, while Lymnium is exclusively so, except for a 
ew intrusive species that inhabit the debatable territory 
between the Nearctic and the Neotropical Regions. Both the 
two groups to which the Galilaean species belong are confined 
to the Palaearctic Region, but several of the allies of U.littoralis 
inhabit south-western Asia. It is to these Asiatic forms that 
U. simonis and U. galilaei are most closely related, whereas U. 
terminalis and the other nominal Species related to or speci- 
fically identical with it exhibit both circum-Mediterranean and 
western Asiatic relationships. 
The absence of such tropical genera as Nodularia and 
Parreysia is a noteworthy feature of the molluscan fauna of the 
Jordan system, and the fact that Unio (s. str.) is not found in 
the Nile must be noted in the same connection. 
This universally distributed family is represented in the 
lake by several Species of Corbicula, a genus widely distri- 
The other forms, C. cor, Lk., C. crassula, Mouss. (possibly 
no more than a variety of C.cor.), C. jacus, Brgt., and 
are alt, moreover, northern forms not known south of the Lake 
of Tiberias, 
