FORAMINIFERA OF THE ATLANTIC OCEAN 133 



rated to form a network; apertures in the early stages as in Planor- 

 bulina, later several on the sides of the chambers, with very short 

 necks. 



Recent. 



This genus is confined to shallow warm waters of the Indo-Pacific. 



Genus PLANORBULINELLA Cushman, 1927 



Planorbulinella Cushman, Coiitr. Cushman Lab. Foram. Res., vol. 3, 1927, 



p. 96; Special Publ. No. 1, 1928, p. 327. 

 Planorbulina (part) of Authors. 



Genoholotype. — Planorbulina larvata Parker and Jones. 



Test in the adult nearly bilaterally sjmimetrical, in the young 

 attached and like Planorbulina, soon having the chambers developed 

 about the periphery in annular series, the chambers of each series 

 alternating with those of the adjacent ones; wall calcareous, coarsely 

 perforate; apertures in the adult, two, one at each side of the chamber 

 in the median line. 



Tertiary and Recent. 



This genus is only known from the Indo-Pacific in the living state. 



In the Tertiary it had a much wider distribution and more complex 



species. 



Genus LINDERINA Schlumberger, 1893 



Linderina Schlumberger, Bull. Soc. Geol. France, ser. 3, vol. 21, 1893, p. 

 120. — Cushman, Special Publ. No. 1, Cushman Lab. Foram. Res., 1928, 

 p. 328. 



Genoholotype. — Linderina brugesi Schlumberger. 



Test similar to Planorbulinella with annular series of chambers, but 

 developing a thick layer of clear shell material over the central por- 

 tion of the test on the two flattened sides; wall calcareous, coarsely 

 perforate; apertures in the adult formed by the coarse perforations 

 of the peripheral border. 



Upper Eocene. 



Genus ACERVULINA Schultze, 1854 



Acervulina Schultze, Organ. Polythal., 1854, p. 67. — Cushman, Special 

 Publ. No. 1, Cushman Lab. Foram. Res., 1928, p. 328. 



Genotype, by designation. — Acervulina inhaerens Schultze. 



Test attached by the dorsal side, at least in the early stages, if 

 attached to a small object often entirely covering it and then covering 

 its own early chambers, earliest chambers coiled; wall calcareous, 

 coarsely perforate; apertures formed by the coarse perforations of 

 the test. 



Late Tertiary and Recent. 



Under this generic name are placed those adherent species which 

 form more or less plate-like encrustations and become irregular in 

 form. 



