66 PROTOZOA. 



Tertiary group in the solid framework of the earth's crust, 

 whether in Europe, Asia, or Africa. It often attains a thick- 

 ness of many thousand feet, and extends from the Alps to the 

 Carpathians, and is in full force in the north of Africa, as in 

 Algeria or Morocco. It has also been traced from Egypt, 

 where it was largely quarried of old for the building of the 

 Pyramids, into Asia Minor, and across Persia, by Bagdad, to 

 the mouths of the Indus. It occurs not only in Cutch, but in 

 the mountain-ranges which separate Scinde from Persia, and 

 which form the passes leading to Cabul ; and it has been fol- 

 lowed still further eastwards into India, as far as Eastern 

 Bengal and the frontiers of China." Another important 

 member of the Eocene Rocks is the Miliolite Limestone of 

 the Paris basin, so called because of the abundance in it of the 

 shells of a species of Miliola, of which a living form is shown 

 in fig. 6, b. 



II. RADIOLARIA. 



The order Radiolaria is denned as comprising those members 

 of the Rhizopoda which possess a siliceous test or siliceous spicules, 

 and are provided -with pseudopodia which stand out from the body 

 like radiating filaments, and occasionally run into one another 

 (fig. 14)- 



Fig. 14. Recent Radiolaria. a Acanthometra; b Haliomma, one of the Poly- 

 cystina, showing the siliceous test and radiating pseudopodia. 



All the Radiolaria possess hard structures in the form of sili- 

 ceous spicules or a siliceous test ; but only one group, viz., 

 that of the Polycystina, has as yet been detected in a fossil 

 condition. The Polycystina (fig. 14, b} are all microscopic 

 organisms very closely allied to the Foraminifera, from which 

 they differ chiefly in the siliceous nature of their skeleton. 

 The test is glassy, composed of flint, perforated by numerous 



