INTRODUCTION. 
The Foraminteera are small shelled animals, mostly microscopic, of simple 
organization, and of very various forms. Their shells are frequently deli- 
cate in structure and elegant in shape. In size there are many less than 
A inch in diameter ; hut there are some among the discoidal Nummulites 
and Orbitoicles that attain a breadth of more than 2 inches ; so also the 
spherical ParTcerici ; whilst the fusiform Loftusia is found to be more than 
3 inches long ; and Eozoon has been estimated to cover a square foot, with 
a thickness of 5 or 6 inches. Their shells consist of carbonate of lime. 
They are found, often abundantly, in sea-sand, both of the shore and 
of shallow and deep waters ; also in the abyssal ooze of the great oceans. 
They are important components in many limestones that have been formed 
of calcareous mud, shell-beds, coral-reefs, &c., in successive oceans at 
different ages of the world ; and they abound in many clays, which have 
been the silts of ancient seas. 
Studied in the living state, Foraminifera are seen to consist of a glairy, 
white-of-egg-like substance, filling the shell, whether it be simple or 
compound — that is, whether composed of one or of many chambers. This 
is extruded also, as delicate fine threads, either from one mouth-like 
aperture (as in Miliola ), from several marginal holes (as in Peneroplis ), 
or from numerous pores all over the shell (as in Rotalici) ; and similar fila- 
ments proceed from a layer of this soft material thrown back over the 
shell in some instances. 
This living gelatinous substance is called sarcode ; and the emitted 
threads are termed joseudojpodia. These being retractile and used for 
locomotion, the creatures are said to belong to the Rhizojooda. 
The pseudopods generally interlace one with another, forming an irre- 
gular network at some distance from the shell. Hence the Foraminifera 
are grouped in classification as the Reticularia. The segments of sarcode 
