32 PROTOZOA RHIZOPODA CLASS i 



into principal chambers by />///><///// i/lm-tn/ *c/ifu, and these are further broken, 

 into second arii diamlx-iictx /<// trti.Htrrw partitions. Septa single or more 

 double. 



Schica ;/<// na, Moll. Test spherical, finely perforated. Primary and 

 secondary septa simple, thin, straight ; secondary chainberlets communicating 

 with the next following principal chamber by means of a basal aperture. 



A, Fiuulinactflndriea, Kisoh. Carboniferous Limestone ; Sarauisk, Russia. Natural size. A C, Same species 

 showing various cross-sections enlarged. D, Enlarged srrtinn showing chambers communicating by means of 

 foramina, (a, 6). 



Abundant in Carboniferous Limestone of Japan, China, Sumatra, North 

 America, and Russia. 



^i/F-usulin-a, 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 in most f units 

 also an anastomosing canal-system occupying inter septal 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, d'Orb. (Fig. 37). Test lenticular, slightly inequilateral, 

 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, d'Orb. (Fig. 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, d'Orb. (Fig. 39). Like Operculina, but with chambers sub- 

 divided by secondary septa into chamberlets. Tertiary and Recent. 



, d'Orb. (Phacites, Gesner ; Leuticulites, Lam.), (Figs. 40-42). Test 



