346 FORAMINIFERA 



the following types are recognized : (a) Outer walls convex, side 

 walls converge to a point or the inner boundary may be formed 

 by the outer wall of a chamber of an inner ring ; the transverse 

 or the radial diameter may be the longer, (b) Type (a) grades 

 into rhomboid or diamond-shaped chambers ; the radial or trans- 

 verse diagonal may be the longer, (c) Spatulate chambers, which 

 have an elongate pointed inner end, more or less parallel sides, 

 and either a curved or an angular outer end ; radially elongate 

 or short, (d) Hexagonal chambers, elongate or short. Al- 

 though for species or even for subgenera, the types of chambers 

 may be characteristic, there is variation, and there is intergra- 

 dation between the different types. Types (a) and (b) are very 



EXPLANATION OF PLATE 58 



Fig. 



1-5. Orbitoides apiculata Schlumberger. X 16. (After H. Douville). 



Early stages of megalospheric individuals showing various 



divisions of the chambers. 



6. Orbitoides media (d'Archiac). X 24. (After H. Douville). Por- 



tion of vertical section showing median chambers and openings. 



7. Simplorbites gensacicus (Leymerie). X 16. (After H. Douville). 



Horizontal section of early chambers of megalospheric specimen. 

 8-10. Lejjidorbitoides socialis (Leymerie). Fig. 8, Central chambers of 

 horizontal section of microspheric form. X 40. Fig. 9, Central 

 chambers of horizontal section of megalospheric form. X 16. 

 Fig. 10, Horizontal section of outer median chambers. X 16. 



11-15. Clypeorbis mamillata (Schlumberger). X 16. (After H. Dou- 

 ville). Figs. 11-13, Horizontal sections of the early chambers 

 at diflferent levels. Fig. 14, Vertical section. Fig. 15, Hori- 

 zontal section showing pillars. 



16, 17. Pseudorbitoides trechmanni H. Douville. (After H. Douville). 

 Fig. 16, Horizontal section of early chambers. X 32. Fig. 17, 

 Portion of vertical section. X 16. 



18. Discocyclina. Diagrammatic horizontal section. (After Van der 



Vlerk and Umbgrove). 



19. Discocyclina (Asterocyclina) stella Giimbel. X 24. (After H. 



Douville). Portion of horizontal section. 



20. Discocyclina (Discocyclina) numynulitica Giimbel. X 16. (After 



H. Douville). Section showing pillars and lateral chambers. 



21. Discocyclina (Discocyclina) archiaci (Schlumberger). X 16. 



(After H. Douville). Horizontal section of early chambers. 



22. Discocyclina (Discocyclina) sennesi H. Douville. X 16. (After 



H. Douville). Horizontal section of early chambers. 



