4-2 



I'AL.liONTOLOGY 



strata, and attain their niaxiniiun size in the older rocks. 

 Minute Ostracoda, related to the recent C//jn is (tig. 10, 5), 

 swarm in the laminated fresh-water clays of the Wealden ; 

 whilst the marine Cythcridce assist with their multitudinous 

 atoms in building up the chalk. Amongst the Phyllopods, the 

 gregarious Estheria covers the slabs of Wealden and of Keuper 

 with crowds of bivalve shells which have been commonly mis- 

 taken for Cycladcs and Posidonomyce. Estheria abounds in the 



Fig. 9. 



Paleozoic Entomostraca. 



1. Leperditia Baltica, Wahl. ; XT. Silurian, Gothland. 



2. Entomoconclms Scouleri, M'C. ; Carboniferous, Ireland. 



3. Beyrichia complicata, Salter ; L. Silurian, Wales. 



4. Dithyrocaris Scouleri, M'C; Carboniferous. Ireland. 



5. Pterygotus Anglicus, Ag. ; Old Bed Sandstone, Ludlow. 



6. Bellinurus bellulus, KiJnig.; Carboniferous, Coalbrookdale. 



7. Ula?nus Davisii, Salter; L. Silurian, Bala. 



8. Phacops caudatus, Broil. ; U. Silurian, Dudley. 



9. Calymene Blumenbachii, Br. ; U Silurian, Dudley. 



10. Trinucleus ornatus, Sternb. ; L. Silurian, Britain. 



11. Agnostns trinodus, Salter; L. Silurian, Britain. 



Caithness flags of the middle Devonian series. The globose 

 Entomoconclms (fig. 9, 2) is found in the carboniferous lime- 

 stone ; Leperditia (fig. 9, 1) in the Silurian rocks of the north ; 

 and Beyrichia (fig. 9, 3), which is characteristically Silurian. 



