326 



PALEONTOLOGY 



last genus is very abundantly represented on modern 

 coral beaches. 



Of the Arenacea the most important are Saccammina 

 (Carb.-Rec.) of one or several spheroidal chambers ; 

 Endothyra (Carb.-Trias.) resembling some of the Rotalidae 

 in form ; and Orbitolina (Cret.) conical, the chambers 

 cyclical in arrangement. Textularia is commonly in- 



FIG. 99. LEPIDOCYCLINA TOURNOUERI, DOUVILLE AND LEMOINE, 



OLIGOCENE. 

 (Megalospheric form.) 



a, Vertical section. (Xis.) b, Part of horizontal section. (Xi8.) 

 (After R. Douvilte and Lemoirie.) 



eluded among Arenacea, but is always perforate and 

 hyaline, at least in early life. 



The Perforata are usually well-preserved fossils, 

 whether in Limestone or Clay, or even in sands in some 

 of the latest formations. The Imperforata, having 

 aragonite tests, are less frequently preserved. A very 

 special mode of preservation is that of internal casts in 



