ORDER I FORAMINIFERA 23 
Foraminifera are divided into the four following sub-orders :—Chitinosa, 
Agglutinantia, Porcellanea, and Vitro-Calcarea, 
Sub-order A. CHITINOSA. Schwager. 
Test chitinous, imperforate, sometimes encrusted with agglutinated particles, and 
with pseudopodial aperture at one or at both extrematies. 
This group comprises the single family Gromidae, which is made up chiefly 
of fresh-water forms, and whose occurrence in a fossil state is unknown. 
Sub-order B. AGGLUTINANTIA. Schwager. 
Test composed of agglutinated sandy particles or other silicious foreign bodies, which 
are held together by a compact, silicious, or argillaceous cement. 
Family 1. Astrorhizidae. Brady. 
Test arenaceous, with rough exterior, usually unsymmetrical, often attaining con- 
siderable size; the sandy particles are sometimes only loosely cemented together ; 
occasionally branching or developing radial prolongations ; septa wanting. 
Recent, and very abundant at great depths. Fossil in Palaeozoic and 
Jurassic formations. 
Saccammina, Sars. (Fig. 13). Shell thick, with labyrinthiform interior ; 
spherical, pear-shaped, or fusiform, with tubular prolongations at one or both 
ends ; sometimes united together in chains. Ordovician (Ayrshire), Devonian 
(Canada), Carboniferous, and Recent. Entire strata of Carboniferous rock 
near Elfhills, Northumberland, are built up by S. Carteri, Brady. 
Large-sized species of Astrorhiza, Psammosphaera, Saccammina, Hyperammana, 
and Rhabdammina are described by Hiiusler from the Upper Jurassic (Trans- 
versarius beds) of Switzerland. 
Family 2. Lituolidae. Brady. 
Test arenaceous or composed of agglutinated particles of various kinds ; more or less 
regular in contour; divided by septa into a number of chambers, or more rarely single- 
chambered ; free-swimming or attached ; septal planes irregular, sometimes labyrinthie. 
Recent species occur mostly at considerable depths. 
Thurammina, Brady. Test free, monothalamous, irregularly spheroidal, 
usually with excrescences or spiny processes. Upper Jurassic and Recent. 
Ammodiscus, Reuss. Test free, monothalamous, depressed, spirally coiled in 
a single plane, with terminal pseudopodial aperture. In all formations from 
Carboniferous to Recent. 
Trochammina, Park. Jones (Fig. 16). Test thin, smooth, consisting of com- 
pact, ochre-like cement with embedded sandy particles ; turbinate, or spirally 
wound like a snail-shell (trochoid) ; imperfectly chambered. Lias to Recent. 
Placopsilina, VOrb. (Fig. 15). Test rough, arenaceous, attached, and 
divided into pyriform or spherical chambers, which are joined in chains or are 
irregularly attached together. Lias to Recent. 
