ORDER II FORAMINIFERA 35 



which canals ai'e not present; solid wedge-shaped deposit of intermediate 



<'&«^, „\^ 



Fig. 27. 



a d 



Nummulifes r.fr. luaisanus Dfr. Eocene ; Kressenberj^, Upper Bavaria. Several times enlarged. 

 a, Mari;inal cord with canal-system ; h, Septal plane with interseptal canal-system ; c, Interior of chamber ; 

 (I, Finely perforate periphery ; e, Small pillars of intermediate skeleton. 



skeleton near the umbilicus. On one side the volutions completely enclose 

 one another as far as the centre, on the other they overlap 

 only partially by means of alar prolongations extending in- 

 wards. Chambers communicate with each other by means 

 of a slit along the basis. Miocene to Recent. Particularly 

 abundant in Miocene. 



Operculina d'Orb. (Fig. 25). Test discoidal, complanate, 

 composed of three to six rapidly expanding spiral whorls, 

 which are polythalamous and non-involute. Septa and 

 marginal cord traversed by a direct canal-system, which gives 

 off numerous branches. Cretaceous to Recent. Particularly 

 abundant in Eocene. 



Heterostegina d'Orb. (Fig. 26). Like Operculina, but with chambers sub 

 divided by secondary septa into chamberlets. Tertiary and Recent. 



Fig; 28; 



Nummulites (Assi- 

 Una) exjmnens Sow. 

 Eocene ; Pyrenees. 



C 3 c 1 2 Fig. 29. 



A '^~, Nummulites (jizchcnslsEhThg. Eocene; Libyan Desert. Natural size. .4 =*, Specimen with eroded peri- 

 pheral portion, showing arrangement of septa. i}i2, Nummulites laevigatus Lam. Calcaire Grossier ; Paris. 

 Natural size. B3, Portion of same enlarged. 6'i2j Nummulites ramondl Defr. Eocene (Nummulitic lime- 

 stone) ; Pyrenees. Natural size. C'3, Enlarged section. 



Nummulites Lam. (Phacites Blumenb. ; Lenticulites Lam.) (Figs. 27-29). Test 



