32 PROTOZOA—RHIZOPODA CLASS I 
into principal chambers by vertically directed septa, and these are further broken up 
into secondary chamberlets by transverse partitions, Septa single or more rarely 
double. 
Schwagerina, Moll. Test spherical, finely perforated. ‘Primary and 
secondary septa simple, thin, straight ; secondary chamberlets communicating 
with the next following principal chamber by means of a basal aperture, 

Fic. 36, 
A, Fusulina cylindrica, Fisch. Carboniferous Limestone ; Saranisk, Russia. Natural size. b, C, Same species 
showing various cross-sections enlarged. D, Enlarged section showing chambers communicating by means of 
foramina (a, b). 
Abundant in Carboniferous Limestone of Japan, China, Sumatra, North 
America, and Russia. 
Fusulina, Fischer (Fig. 36). Test fusiform, laterally elongated like 
Alveolina, coarsely perforated. Septa of principal chambers undulating, and 
united so as to form secondary chamberlets. Excessively abundant in 
Carboniferous Limestone of Europe (Russia), Asia, and North America, 
Family 6. Nummulinidae, Carpenter. 
Test calcareous, finely perforated, lenticular or discoidal, often attaining consider- 
able dimensions ; polythalamous, and composed either of discoidal spiral whorls or of 
cycloidal rings. Pillars of compact intermediate skeleton present, and im most forms 
also an anastomosing canal-system occupying interseptal spaces and certain other 
portions of the shell. 
Archaediscus, Brady. Test lenticular, unsymmetrical, spirally coiled. The 
segments irregularly constricted and expanded so as to form chambers. Septa 
and canal-system wanting. Carboniferous Limestone. 
Amphistegina, VOrb, (Fig. 37). Test lenticular, slightly imequilateral, 
spirally rolled. Whorls divided into chambers by numerous single septa in 
which canals are not present; solid wedge-shaped deposit of intermediate 
skeleton near the umbilicus. On one side the volutions completely enclose 
one another as far as the centre, on the other they overlap only partially by 
means of alar prolongations extending inwards. Chambers communicate with 
each other by means of a slit along the basis. Miocene to Recent. Par- 
ticularly abundant in Miocene. 
Operculina, VOrb. (Big. 38). Test discoidal, complanate, composed of three 
to six rapidly expanding spiral whorls, which are polythalamous and non- 
involute. Septa and marginal cord traversed by a direct canal-system, 
which gives off numerous branches. Cretaceous to Recent, Particularly 
abundant in Eocene. 
Heterostegina, VOrb. (Fig. 39). Like Operculina, but with chambers sub- 
divided by secondary septa into chamberlets. Tertiary and Recent. 
Nummulites, VOrb. (Phacites, Gesner ; Lenticulites, Lam.), (Figs. 40-42). Test 
