102 PROTOZOA. 



with a flinty agglutinate shell ; Haliphyscma, a form utilising sjDonge 

 spicules to cover itself, once mistaken for a minute s]ionge, or f<")r a ver}' 

 simple many celled animal. 



Most kinds of chalk consist mainly of the shells of Foraminifera, 

 accumulated on the floor of ancient seas ; Ntuiivnililes and related fossil 

 forms were as large as shillings or half-crowns. 



7. Radiolaria. — Marine Rhizopods, divided by a membrane into an 

 inner central capsule (with one or more nuclei), and an outer portion, 

 giving off radiating thread-like pseudopodia. The protoplasm of the 



Fig. 2S.— a pelagic Yox^mmikx—Hastiocrina [Glohigei-ina] 

 Murrayi. (After Brady. ) 



Note central stiell, projecting c.-ilcareous spines witti a protoplasmic 

 axis ; also fine curved pseudopodia and \acuolated protoplasm. 



two regions is connected by openings in the capsule membrane, and 

 contains many vacuoles. No contractile vacuoles have been seen. ' 



There is usually a skeleton, in most cases siliceous and of complex 

 architecture, in some cases of a horn-like substance, called acanthin 

 The skeleton may be quite outside the central capsule, or may invade it 



