ORDER I FORAMINIFERA 35 
primordial spiral of three to five whorls. The rings are divided by transverse 
partitions into small rectangular chambers, and the septa and marginal cord are 
traversed by canals. Superimposed over the median series of principal 
chambers on both sides are several layers of flattened secondary chamberlets, 
D 
Cc. She 
SCHWAGER Pi lig a Bs]: 

Fic. 45. 
A, Orbitoides papyracea, Boubée. Eocene (Ferruginous sandstone); Kressenberg, Upper Bavaria. (Greatly 
enlarged). 1Median chambers; 2 Lateral chambers ; ? Compact pillars of intermediate skeleton. , Portion of 
median transverse section, highly magnified; 2 Lateral chambers with perforate walls; 4Canal-system of 
cyclical marginal cord; 5Tubules connecting adjacent chambers. C, Periphery and profile of same, natural 
size. D, Orbitoides tenella, Giunbel. Eocene; Kressenberg. (Natural size.) 2, Orbitoides variecostata, Giimbel. 
Eocene; San Martino, near Verona. (Natural size.) F, Orbitoides ephippium, Sow. Eocene; Kressenberg. 
(Natural size.) 
which are likewise disposed in concentric rings. Very abundant in the Eocene, 
associated with Nummulites ; rare in Upper Cretaceous and Miocene. 
Dawson, Carpenter, and various other authors have referred the so-called 
Eozoon occurring in crystalline limestone of the Archaean (Laurentian) period 
to the Foraminifera; but the elaborate investigations of Mobius have shown 
that neither Hozoon nor Archaecosphaerina can be regarded as organic structures, 
but are mineral segregations. 
Range and Distribution of Fossil Foraminifera. 
Of the over 2000 species of Foraminifera that have been described, about 
two-thirds are known in a fossil state. The longevity of certain genera and 
species is remarkable, many of them persisting, according to Parker, Jones, 
Brady, and others, throughout a number of formations of various ages. 
The earliest forms occur very sparingly in the Silurian of St. Petersburg, 
Siberia, and Scotland. They are for the most part poorly preserved, those 
from Petersburg being recognisable only as glauconitic casts, belonging in 
part to silicious shell-bearing genera (Placopsilina, Saccamina), and in part to 
vitreo-perforate genera (Nodosaria, Lagena, Globigerina, Rotalia). The Devonian 
is also very poor in Foraminifera remains ; but, on the other hand, the Carbon- 
iferous yields an abundant and considerably varied fauna; in fact, certain 
genera (Fusilina, Schwagerina, Saccamina, Endothyra) build up limestone de- 
