Vol. XI, Nos. 10 & 11.] The Fauna of the Jordan System. 459 
[V. eae 
UNIONIDAE. 
ere is probably no family of molluscs in which the shell 
is more liable to slight changes in size, shape, texture and 
colour, in correlation with environment, than the Unionidae, 
and consequently an enormous number of species been 
described, many of which are mere phases or aberratio In 
Preston’s ‘‘ Faunal List’? no less than seventeen names of 
nominal ‘species of Unio occur. According to the synonomy of 
impson’s! ‘‘Synopsis of the Naiades’’ these may be reduced 
to nine or ten, but it does not appear that the latter author 
was personally acquainted with the Jordan forms. In my own 
collection seven nominal species are ic aiaeie They are U. 
pietri, U. tristrami, U. terminalis, U. prosacrus, U. simonis, u 
galilaet and U. chinnerethensie the last being a new species rep- 
resented by many specim 
‘These “ species ’ ie an observer who is not a professed 
conchologist, seem to fall into three groups, or at any rate into 
two groups and one sub-group as follows :—U. pietri, U. tris- 
trami, U. terminalis, and U. prosacrus zits one eroaPy with 
U. chinnerethensis clearly distinct but not far oved 
from them; and U. simonis and U. galilaei mhadlcerify 
distinguished by their much thicker and more nearly circular 
shells. Of the species of the first group I can clearly 
alee s new species, seem to me to be i aca. 
According to Simpson, U. tberiadensis, U . tristrami, 
U. semitru ugatus, Lamarck, a form described from Asia Minor. 
Tristram ,? moreover, does not regard U. terminalis as specifically 
distinct ‘from either U. jordanicus or Lea’s ignatus from 
the Tigris. Further, Simpson himself points out that Lea and 
érussac were of the opinion, after examining Lamarck’s 
Specimens, that U. semirugatus was not distinct so 
U. littoralis of the same author, a circum-Mediterranean speci 
with which Simpson regards U. requieni, Mich. (a widely fiatri. 
buted form said to have been found in the lake) as synony- 
mous 
s useless to follow the synonomy of the nominal species 
of Unioniles further, but interesting results become apparent 
1 Proc. U. S. Nat. Mus. (22), PP. 501-1044 (1900). 
2 Hone W. Palestine, p- 201 (1888). 
