PROTOZOA OR SIMPLEST ANIMALS. 9 



(Imperforata, Fig. 4), or have, in addition to the main apertiu'e, the High Wall 

 wall of the shell perforated by numerous pores (Perforata, Fig. 5). ^^^se 

 Calcareous imperforate shells (see Family II.) have an opaque white GaUery? 

 porcellanous appearance, and perforate shells, in their early stages, 

 a vitreous appearance (Families V. to X.). The shell may consist of 

 one chamber {Lagena, Family VII.), or of many, arranged in linear, 

 spiral, or concentric series, or on each side of a middle line. 



In Glohigerina, Rotalia, &c. (Family YIII. and IX.), all the 

 chambers of the " rotaliform " spiral are visible from above, but 



Fig. 7. 



Shells of Glohigerina, showing lower and upper surface. Magnified. 



only the last coil from below. In NummnUtes (Family X. and 

 Introductory series) the last coil of the spiral wholly encloses all the 

 preceding coils. 



Although many of the specimens in the Case are very small, yet, 

 with the aid of the diagrams, the shape can frequently be made out ; 

 in some species the shells attain to relatively immense proportions, 

 as Ggcloclypeus carpenterii (Family X.). from Borneo, with a thin 

 discoid shell over two inches in diameter. 



The Foruminifera have played an important part in forming 



