Vol. X1, Nos. 10 & 11.] The Fauna of the Jordan System. 455 
[N.S.] 
every respect, but crumble into a white powder as soon as they 
are removed from water. 
or the statements as to the geographical and geological 
distribution of genera givenin the following notes, I am indebted 
mainly in the first instance to Fischer’s valuable Manuel de 
Conchyliologie et de Paléontogie Conchyliologique (Paris : 1887). 
LIMNAEIDAE. 
Limnaea auricularia, Linn. and L. virginea, Preston repre- 
sent this family in the fauna of the lake-basin, but speci- 
mens of the former species were taken only in the Jordan a few 
hundred yards above its entry. The species is essentially a 
including Siberia. L. virginea is only known from the Jordan 
channel in the southern part of the lake, in which it is the 
only non-operculate Gastropod as yet found, and from a small 
stream in the Wad-es-Semakh near the eastern shore. 
PHYSIDAE. 
The only representative of this family in Mr. Preston’s list 
is Physa tiberiadensis, a new species found with Limnaea 
auricularia in the Jordan and therefere not actually belonging 
to the lake-fauna. Both Physa and Limnaea are cosmopolitan 
genera. 
MELANUDAE. 
Individuals of two genera are common in the lake, namely 
Melania and Melanopsis. 
The former is mainly a tropical genus, abundantly repre- 
sented in the Ethiopian and Oriental Regions and occurrin, 
alsoin tropical America. Itsclaim to be regarded as Palaearctic 
is founded on a few intrusive species. As a genus it makes its 
appearance in Cretaceous deposits and is well represented in 
the Tertiary; Jurassic species assigned to it are, according to 
Fischer, of doubtful position. 
Melanopsis, on the other hand, occurs most abundantly 
n 
ably Palaearctic origin. It dates from the Crag. Two sec- 
tons of the genus an found in the Lake of Tiberias, viz. 
Melanopsis (s. s.) and Canthodomus, Swainson. 
Melania is probably represented by a single species, J. 
tuberculata, Miiller, of which M. rothiana, Mousson, appears 
to be a synonym, if it is not identical with the variety elongata 
of Locard. ‘The typical form of the species has perhaps a 
