APPARENTLY CORRELATED TO THE CONDITIONS OE LIFE. 
.31 f) 
In the eastern lake (No. 2) were great numbers of living Cockles. In texture 
these shells resemble those of Ptamleh Lake No. 1, though the tendency to ribbing 
on the inside was not so much marked, being generally slightly present behind the 
10th to 12th rib. The colour of the outside of the shells is yellowish-white almost all 
over, but on the inside the region of the posterior 3 to 6 ribs is chocolate colour, but the 
rest of the inside of the shells has the same brig-ht white colour as in Ramleh Lake 
No. 1. The proportion of length to breadth is very great in these shells. In 30 
shells varying in length between 29 mm. and 16'5 mm. the average ratio of length 
to breadth is 1 : 0‘657, and in 30 shells varying in length between 21 mm. and 17 mm. 
this average ratio is 1 : 0'66.5. It is a remarkable fact that in the case of these shells 
the increased proportional length is almost as much marked among the small shells as 
it is amongst the large ones, and, as may be seen in Table VI. (a), this feature is 
present fairly uniformly in nearly all the individuals. 
Another character of these fresh-water shells is the frequent occurrence of specimens 
with the free ventral margins of the shell bent inwards, as shown in Plate 26, fig. 13. 
Recapitulation [Mctreotis and Ramleh Lakes). 
The shells found in the Mareotis and Ramleh district were of four kinds ; (l) 
ancient shells, like the ancient shells of Abu Kir; (2) shells lately extinct (?) in 
Mareotis itself. Though the conditions under which these animals lived cannot be 
positively stated, it is nevertheless clear that they lived in shallow water, and 
that_ this water received in winter a great volume of fresh water from the Nile, 
being then probably brackish, while it is likely that in summer it was rather salter 
than the sea. 
The shells having lived under these conjectural conditions have definite characters, 
being long, thin, highly coloured shells. 
From them are descended independently (3) the Cockles of Ramleh Lake No. 1, 
and also (4) the Cockles of Ptamleh Lake No. 2. Both (3) and (4) have been living- 
in more or less completely fresh water for some time, and, on comparing them with 
(2) , they will he found to differ from them similarly, and to resemble each other in 
most respects. They are both fairly thick and coarse, and the high colour of the 
Mareotis shells is much reduced in (3), and still more so in (4). 
The feature of great proportional length remains in both. 
As was found in the case of the various samples of Aral shells, the samples of each 
locality are distinct and easily recognisable, but, excepting a slight difference iu colour, 
(3) and (4) are very nearly alike. A few specimens among (2) resemble in colour 
those of (3), but they are quite different in texture. 
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