134 



Guide to the Tnvertehrata. 



GALIEEY and arenaceous forms. Perhaps the hest-known example of a 



^' foraminiferal limestone is the White Chalk which is found over 



^^h\^^ large areas of this country, France, Ireland, and Denmark. It 



casel6. is largely formed of the entire and fragmentary tests of numerous 



genera of microscopic Eoraminifera, of which the most common 



arc Glohigerina, Textularia, Rotalia, and Nodosaria. 



In the Tertiary rocks also many extensive limestone strata are 

 principally composed of Foraminifera, as, for example, the Mdiola 

 limestone of the Paris Basin and the South of Prance ; other 

 Eocene limestones are filled with the tests of Aheolina, Orhitolites, 

 and Orhitoides ; but by far the mo&t noted are the Nummulitic 

 limestones of the Mediterranean area, the Carpathians, Hungary, 

 Crimea, Egypt, Persia, and India (Fig. 182). 



Fig. \^2.—Nummulinanummi(laria,W0xh. ^, the shell viewed externally. B, 

 the same horizontally bisected. C, the same vertically bisected. 1), vertical 

 section of part of the shell, highly magnified, showing the chambers of the 

 median plane, the alar prolongations, and the tubuli of the shell substance. 

 Eocene Tertiary. (Nicholson's Palaeontology.) 



Recent deep-sea explorations have proved that beds of Fora- 

 minifera analogous to those of the Chalk are now being formed 

 over wide areas of the sea-bottom. 



In the upper portion of the Wall-case 9 there is a series of 

 models of 100 different forms of Foraminifera, prepared by 



