70 



POST-TERTIARY ENTOMOSTRACA. 



and L. pyymcba, with one of Ostracoda, viz. Cytheridea punctillata, Brady, which was a 

 perfect specimen with united valves. 



25. DipPLE Tile-works, Three Miles East of Girvan. 



The clay in this deposit is remarkable for the character of its fauna, as showing a 

 direct passage from marine through estuarine to freshwater conditions. 



Freshwater, brackish, and marine forms are not mixed up promiscuously together 

 from bottom to top, but the fauna is nearly pure marine at the bottom, brackish in the 

 middle, and almost entirely freshwater at the surface. Three samples of the clay were 

 examined. 



The uppermost part, between six and nine feet below the surface, is distinctly 

 laminated, and of a dark mottled appearance. Together with some vegetable remains it 

 contains a great abundance of the chitinous parts of Daphniadse and Lyncseidae, various 

 forms of Cypridse, and other genera and species which have a greater or less aptitude for 

 existence in brackish water, such as Limnicythere inopinata, Loxoconcha iamarindus, and 

 Cythere tenera. 



Some shell fragments are associated with the Ostracoda, — possibly of Mytilus edulis^ 

 which can exist at high-water-mark, and would be lifted up with the sea-bottom when it 

 was placed in a position to become a freshwater pool. 



Under this freshwater clay we find four feet of clay of a uniform grey colour, in 

 which the brackish water forms are very largely developed. A few freshwater species 

 occur, such as Sphcerium corneum and Cypris gibha ; but brackish water forms, such as 

 Cythere castanea (which is very abundant), greatly prevail. The appearance of Utriculus 

 obtusus and Homaloyyra atomus also shows that the clay is beginning to assume a more 

 decidedly marine character. 



In the succeeding three feet of clay the freshwater and brackish organisms have 

 almost disappeared, and the Mollusca are far more numerous, both in species and indi- 

 viduals, than in any of the overlying strata. Taking them in the prevailing order, they 

 are : 



Homaloyyra atomus . . , Very common. 



Bissoa striata ■ . . . Moderately common. 



Utriculus obtusus . . . Moderately common. 



Leda pyymcea .... Moderately rare. 

 Axinus Jlexuosus . . . Three valves. 



Slcenea jplanorbis . . . One valve. 



