ORDER II 



FORAMINIFEEA 



39 



Fabularia Defr. (Fig. 35). Like BUoculina, but relatively larger. General 

 aperture cribriform ; chambers not an empty cavity, but filled with porcell- 

 anous or calcareous matter, and perforated by numerous anastomosing canals 

 which are directed parallel with the axis of convolution. Abundant in the 

 Eocene of the Paris basin. 



Vertebralina d'Orb. (Fig. 36). First-formed portion of test consisting of 

 coil-shaped loops, the segments afterwards becoming joined in rectilinear 

 series. Tertiary and Recent. 



Idalina Schlumb. Last -formed chamber completely enveloping all pre- 

 ceding ones. Cretaceous. 



Subfamily E. Peneroplinae Brady. 



Test planospiral or cyclical, and bilaterally symmetrical ; apertures many. 



Peneroplis Montf. (Fig. 37). Test discoidal, complanate, polythalamous ; 

 direction of growth primarily spiral, gradually becoming rectilinear, while 

 rapidly increasing in width. Septa perforated by numerous pores. Tertiary 

 and Recent. 



''^'EW M 



^Ei 



aS^ 



Fid. 37. 



PeiicroplU plawitus 

 Montfort. Rpccnt ; 

 Mediterranean. 



Fig. 38. 



Orhicul ina nummi.f- 

 malis d'Orhigny. Plio- 

 cene ; Sienna, Italy. 



Fir.. 39. 



A, OrhitoUfcs complanafa Lam. Eocene (Cal- 

 caire Grossier) ; Paris. B, Portion of same en- 

 larged. 



Orbiculina Lam. (Fig. 38). Test discoidal, first -formed portion spiral, 

 afterwards becoming annular ; polythalamous ; septation regular, chambers 

 subdivided ; septa and walls of segments perforate. Tertiary and Recent. 



Orbitolifes Lam. (Fig. 39). Test discoidal, circular in outline, both surfaces 

 slightly concave in the middle, attaining comparatively lai'ge size, and com- 

 posed of segments which are arranged concentrically about a few spirally 

 coiled primordial chambers. Septa radially disposed, and perforated by 

 symmetrically placed pores. In the more complicated forms the principal 

 segments are invested with a superficial multilocular layer, the chambers of 

 which are also arranged in concentric rings and communicate with the 

 principal segments by means of pores. An important rock-building genus, 

 ranging from the Lias onward. 0. praecursor and 0. circumvulva Giimbel are 

 Jurassic, 0. macropora d'Orb. Cretaceous, and 0. complanata Lam. Tertiary 

 species. 



Subfamily F. Alveolininae Brady. 



Test spiral, elongated in the direction of the axis of coiling ; chambers divided 

 into secondary chamberlets. 



Alveolina d'Orb. (Borelis Montf.) (Fig. 40). Test fusiform, elliptical or 

 spherical, usually elongated in the axis of convolution, and composed of 



