Vol. XI, Nos. 10 & 11.] The Fauna of the Jordan System. 457 
[N.8S.] 
that the local race of the lake is the same as that of Lake 
Huleh- In any case both species are stated by some authori- 
ties to be widely distributed in Syria, and M. praerosa at 
any rate, although it is found in certain parts of the lake not 
uncommonly, is a fluviatile rather than limnic species. Daut- 
zenberg regards the two forms as synonymous, and this view 
is probably correct. The distribution of M. praerosa (s. 1.) is 
mainly North African. 
Considering the local representatives of the Melaniidae as 
a whole we may therefore say that the following faunistic 
elements can be distinguished among them:—(a) a tropical 
element, represented by Melania tuberculata, (b) a Mediterra- 
nean element, represented by Melanopsis costata, and by M. 
praerosa or by M. buccinoidea—if the two latter are distinct. 
HYDROBIIDAE. | 
mong the Gastropods the Hydrobiidae are the dominant 
family in the lake, if by this term we mean the one represented 
by most species. As regards the number of individuals, 
however, the Melaniidae and the Neritidae are better repre- 
sented, for individuals of Melanopsis costata and Theodoxis 
jordani together outnumber those of all other species. In Mr. 
Preston’s list the Hydrobiidae are represented by three genera 
and nine species: all the species are small and scarce, or at any 
rate by no means abundant. The three genera are Pyrgula, 
Bithinia and Bithinella. 
ula is a small genus found mainly in south-eastern 
Europe and in particular in the countries around the Adriatic. 
It occurs in upper Tertiary deposits in the same countries 
and in those of the Levant. 
Bithinia lives practically all over the old world and is first 
found in Tertiary deposits. 
The recent distribution of Bithinella is more restricted and 
its origin probably more recent ; some species occur in brackish 
water. 
of Homs, at Damascus and elsewhere in Syria, B. gennesareten- 
sis, and B. semakhensis, Preston, both apparently endemic 
in the lower parts of i 
Bithinella has five Tiberiad species, that is to say more 
than any other Gastropod genus. Only one of them (Bithinella 
