ORDER I 



FORAMIXIFERA 



33 



symmetrically lenticular or discoidal, composed of numerous spindly arranged 

 polythalamous volutions, and usually with columnar intermediate skeleton, 

 which forms small excrescences on the periphery. The septa and marginal 



FIG. 37. 



.1 mpli istfjina Haueri, d'Orb. 

 Miocene (Leithakalk) ; Nuss- 

 dorf, near Vienna. ", Exterior 

 views, enlarged ; b, Natural 

 si/i 1 ; c, Median section, 

 greatly enlarged ; d, Trans- 

 action, greatly en- 

 larged. 



0-perculina complanata, Bast., sp. Miocene ; 

 Bordeaux, a, Natural size ; 6, c, Median and 

 longitudinal sections, greatly enlarged. 



Heterostegina costata, d'Orb. 

 Miocene (Leithakalk) ; Nuss- 

 dorf, near Vienna. 



cord contain a coarse, anastomosing canal-system, as in Opercnlina. Primordial 

 chamber spherical, sometimes large, sometimes exceedingly minute in size. 

 The whorls either merely embrace one another (Assilina) (Fig. 41), or they 

 completely envelop one another by means of alar prolongations reaching 



FIG. 40. 



cfr. Lucasanus, Dfr. Eocene; Kressenberg, Upper Bavaria. Several times enlarged. 

 a, Marginal cord with canal-system ; i>, Septal plane with interseptal canal-system; c, Interior of chamber; 

 /. 1'im-ly perforate periphery ; e, Small pillars of intermediate skeleton. 



in \vards to the centre (Nummuhna). The septa are pierced in the median, 

 plane by an oblique slit-like aperture, and also extend into the saddle-shaped 

 ilar prolongations of the chambers. They are directed in the groups Jfnifiafat 

 and tftriatae in straight or slightly curved lines (Figs. 40 and 42, C) in the 

 tfhniiifae they follow meandering courses (Fig. 42, A}-, and in the Itrfii-Hlnfn,- 

 (Fig. 42, B) they form an interlacing network by means of connecting pro- 

 VOL. I D 



