PROTOZOA. FORAMINIFERA 23 



Lituola. Shell free, composed of coarse grains, spiral or 

 crosier-shaped. Septa labyrinthine. Aperture simple or sieve-like. 

 Carboniferous to present day. Ex. L. nautiloidea, Chalk. 



Orbitolina. Shell partly sandy, conical or flattened, with 

 convex upper, and usually concave lower surface ; consisting of 

 central compressed chambers surrounded by concentric rings of 

 chambers. Cretaceous. Ex. 0. concava, Upper Greensand. 



Endothyra. Shell free, spiral )similar to Rotalia) ; chambers 

 numerous, composed of an outer calcareous, perforated layer, and an 

 inner compact layer formed of small grains cemented together. 

 Aperture at the inner margin of the last chamber. Carboniferous 

 to Trias. Ex. E. bowmani, Carboniferous Limestone. 



Textularia. (fig. 3, E.) Shell arenaceous (in the small forms 

 it is vitreous) ; form variable, conical, pyriform, or cuneiform ; 

 composed of numerous chambers in two alternating parallel series. 

 Aperture slit-like on the inner edge of the last chamber. Cambrian 

 to present day. Ex. T. globidosa, Chalk. 



III. Vitreous Forms. 



Shell of calcite, vitreous, perforated by numerous 

 minute canals for the passage of the pseudopodia. 



Lagena. (fig. 3, F.) Shell unilocular, very finely perforated. 

 Form globose, ovate or flask-shaped. A single terminal aperture, 

 sometimes at the end of a long neck ; rarely two apertures. Surface 

 smooth, ribbed, striated, or spinous. Cambrian to present day. 

 Ex. L. striata, London Clay to present day ; L. sulcata, Silurian 

 to present day. 



Nodosaria. (fig. 3, H.) Shell composed of a number of 

 chambers which are circular in transverse section, arranged in a 

 straight line, and separated by constrictions. Aperture at the apex 

 of the last chamber. Surface smooth or ornamented with granules, 

 spines, or ribs. Cambrian to present day. Ex. N. zippei, Gault 

 and Chalk. 



Cristellaria. (fig. 3, G.) Shell compressed, lenticular or 

 elongate, multilocular, coiled in part or entirely in a plane spiral ; 



