THE CYPRIS AND ITS FOSSIL ANCESTORS, 85 
Purbeck and Wealden formations are mainly composed of brackish 
and fresh water deposits, and represent a period when the physi- 
cal geographical aspect of the south of England was much different 
to that at any preceeding or succeeding age,—a period when all 
the coast, stretching from Folkstone down to Eastbourne, was the 
mouth of a great river, and for many miles inland an enormous estu- 
ary. This great river received all the sand and muddy sediments 
derived from the degradation of land stretching up to the North 
and North-west, which land yielded enormous quantities of clay 
and clayey loam. ‘These clays and loamy deposits in this estuary 
became worked by torrents and tidal actions into shallows and 
pools, which became the homes and feeding grounds of the Ostra- 
coda, consequently of the Cypris, which flourished and cast their 
valves in vast quantities. Some of these brackish water-beds are 
twenty feet thick, and abound with Cypris. The fresh water marls of 
the Lower Purbeck yield Cyfris Purbeckensis and Cypris punctata, 
whilst in the middle Purbeck, in the fresh water strata, we come 
upon the more remarkable Cypridean forms, viz., Cypris striato- 
punctata, Cypris fasiculata, and Cypris granulata. These have 
been found along with the remains of turtle and fish. 
The Cypris striato-punctata has wavy markings arranged con- 
centrically all over its valves, and the C. fasiculata and C. granu- 
/ata have tubercles at each end only of each valve. 
In the Upper Purbeck we meet, in a fresh water bed of fifty feet 
thick, with forms much like the preceeding, viz., Cypris gibbosa, 
C. tuberculata, and Cypris leguminella. 
In the Wealden proper we have a form of the Cypris called 
Cy pris spinigera, so plentifully deposited throughout the fresh water 
clays as to give a laminated appearance similar to mica. In this, 
and the Purbeck, the remains of the Cypris are so great as to form 
of themselves a deposit of two or three inches thick—a deposit 
mainly composed of the valves accumulated in layers upon the 
soft, fine muds. 
Space will not permit us to trace in further detail the fossil 
ancestors of the living Cypris ; sufficient, however, has been brought 
forward to show that its tribe has existed through countless ages 
and that although the markings of its valves show variations and 
modifications, at different periods, notably in the Purbeck series, 
its fundamental character has undergone no material change. 
True, by comparing the indented structure of the valves of the C. 
Seyrichia with the wavy markings of the C. striato-punctata, or with 
the typical pittings of the C. tuberculata, we see wide differences, 
and would be inclined to consider it a great change in character, 
yet, nevertheless, the general form is maintained throughout. Of 
course as the anatomical parts of the Cypris are too delicate to 
resist decay, we have in all cases been obliged to fall back upon 
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