20 PROTOZOA. FORAMINIFERA. 



composed of numerous chambers in two alternating 

 parallel series. Aperture slit-like on the inner edge 

 of the last chamber. Carboniferous to present day. 



Globigerina. (fig. 2, /, K.) Test calcareous, vitreous, 

 perforated by large canals. Multilocular, chambers glo- 

 bular, few, arranged in a plane or helicoid spiral, each 

 chamber opens by a large aperture into a large central 

 cavity. No supplemental skeleton. Trias to present day. 



Rotalia. (fig. 2, L, M.} Test calcareous, very finely 

 perforated, multilocular. The chambers arranged in a 

 helicoid spiral, so that on the upper surface all the whorls 

 are seen, on the lower, only the last one. The aperture is 

 in the form of a curved fissure on the lower surface of the 

 last segment. The septa are generally double. A supple- 

 mental skeleton is sometimes present. Upper Jurassic 

 to present day. 



Nummulites. (fig. 3.) Test calcareous, lenticular 

 in form, and composed of a large number of whorls coiled 



cb d i 



FIG. 3. Nummulites, showing vertical and horizontal sections, a, mar- 

 ginal cord, with system of canals; b, septum, with canals; c, cham- 

 bers; d, test; e, pillars coming from the supplemental skeleton. 

 (After Zittel.) 



