326 FORAMINIFERA 



nated as Webbina breoni Terquem and Piet, (Mem. Acad. Imp. 

 Metz, vol. 42, 1862, p. 458, pi. 6, figs. 18a-h) . 



In this family which has been derived from the Rotaliidae, the 

 aperture appears first in the median line with the bilateral test 

 of Anomalina, then as the test becomes plano-convex and attached 

 by the dorsal surface, the aperture swings over to the dorsal side. 

 In Cyclocibicides and Cibicidella, genera of the Mediterranean 

 especially, there is an added structure, annular in one and irregu- 

 lar with flask-shaped chambers in the other. Webbina is prob- 

 ably a degenerate genus belonging here. From this family came 

 the attached forms placed in the families Homotremidae and 

 Rupertiidae by the development at right angles to the area of 

 the attachment. 



FAMILY 42. PLANORBULINIDAE 



Test, in the early stages, coiled, attached by the dorsal surface, 

 chambers in a spiral arrangement, apertures single, later with 

 the chambers added in annular series, the apertures usually two 

 to a chamber, the test free and becoming bilaterally symmetrical, 

 not developing pillars. 



KEY TO THE GENERA 



I. Test plano-convex or globular, not bilaterally symmetrical. 



A. Chambers definitely in one plane. 



1. Chambers closely gi'ouped Planorbulina. 



2. Later chambers forming a reticulate network. 



Planorb2dino{des. 



B. Chambers piled up irregularly or in a spherical mass. 



1. Chambers few, hemispherical, test compressed and attached. 



Ace7'vulina. 



2. Chambers numerous, compressed, test globular, free. Gypsina. 



II. Test bilaterally symmetrical. 



A. Sides papillate but not greatly thickened Planorbulinella. 



B. Sides with a very thick secondary mass .Linderma. 



Genus PLANORBULINA d'Orbigny, 1826 



Plate 50, figures 9, 10; plate 51, figure 8 

 Genotype, by designation, PlanorbiiUna mediterraneanfiis d'Orbigny 

 Planorbulina d'Orbigny, Ann. Sci. Nat., vol. 7, 1826, p. 280. 



