APPARENTLY CORRELATED TO THE CONDITIONS OF LIFE. 
309 
The size of tlie beaks is reduced, just as in the case of the Sliumisb Kul shells. 
The shells of the outermost deposit at Jaksi Klich are, as stated above, rather mixed 
in character. I found, however, one locality towards the southern end of the lake 
where the bank was comparatively steep, and from this place I obtained a fairly 
uniform sample. These shells are thin as compared with Cockles of the Aral Sea, but 
thicker than those of the lower deposit of Jaksi Klich. From the latter they differ 
also in not being' highly coloured and in having the beaks fairly developed, though 
diminished relatively to those of normal Aral shells. As will be shown hereafter, they 
very closely resemble those shells which w^ere found on the shore of the lagoon Abu 
Kir, in Egypt ; the length of these shells is as great in proportion to their breadth as 
it is in those of the fourth or fifth terrace at Shumish Kul. The average ratio of 
length to breadth in 30 shells varying in length between 22 mm. and 17 mm. is 
1 : 0‘740 ; that is to say, that the average breadth of a shell 20 mm. long is 14'8 mm. 
Many examples of Ilydrobia vivas were found amongst these modified shells, but 
they do not differ from those of the Aral Sea. 
In attempting to realise the conditions under which the Cockles lived in Jaksi Klich 
before the separation of this series of lakes from the Aral Sea, the fact of its situation 
must be borne in mind. It was a large lagoon, ten miles long and three miles broad, 
very shallow, and connected with the main body of the Aral Sea only by a narrow 
and shallow channel at Ak Jalpas. Hence the conditions of life in it, in a climate 
which undergoes the greatest extremes of heat and cold, must have been always very 
different from those prevailing in Shumish Kul, which had a considerable depth, and 
so must have maintained a much more constant temperature. 
Before, therefore, the communication between the lakes and the Aral Sea was 
interrupted it is clear that the water of Jaksi Klich must have been sometimes very 
hot, and, from the consequent evaporation, it was probably in summer much salter than 
the nearest parts of the Aral Sea. In view then of the obvious correlation between 
the effects of the diminution in size of Shumish Kul and the increase in the propor¬ 
tional length and thinness, &c., of the shells found there, it appears reasonable to 
ascribe these appearances in the shells of the outer deposit at Jaksi Klich to similar 
causes, and these must of necessity have existed, consequent upon the peculiar 
situation and shallowness of the basin. 
All these aj^pearances, as has been shown, became greatly intensified in those shells 
which lived in it during the period after the separation from the Aral Sea. 
Besides the shells in these two deposits, there were found at Jaksi Klich a few 
shells of an entirely different character. These were very large and very thick shells, 
generally occurring in pairs, more or less buried in the sand, though without ligaments. 
The length of these shells was about 30 to 35 mm. ; they almost all show the feature of 
great proportional length and large beaks, and were always found in groups of ten or 
twelve, lying between the outer and inner deposits. These shells are all much worn. 
I shall allude to these shells as “ great shells.” Similar shells will be shown to have 
