Fig. 13. 

 Orbitolina eoncava Lam. 



ORDER II FORAMINIFEEA 27 



Subfamily E. Orbitolininae. 



Test siliceous, imperforate, crateriform and composed of concentric annuli which 

 are partitioned off into numerous chambers. 



Orbitolina Lam. (Fig. 13). Test composed of agglu- 

 tinated sandy particles ; bowl - shaped to depressed 

 conical ; upper surface convex, lower slightly concave ; 

 externally smooth or with concentric bands. Test 

 composed of multilocular rings, the chambers com- 

 municating with one another on all sides by pores. 

 The outer portion of each chamber is subdivided by 

 two secondary partitions disposed at right angles to cenomanian ; Urscheiau, 



, , -^-^ '- , -jiT 1 TT Bavarian Alps, a, Inferior 



each other. Very abundant in the Lower and Upper surface; 6, Superior sur- 

 Cretaceous. 0. lenticularis and 0. eoncava Lam. fenLVgedT"''''''' '''^'°° 



Family 4. Textulariidae Schiiltze. 



Test either arenaceous or calcareous, perforate, the chambers usually numerous, 

 essentially biserial or triserial, or in some genera spirally arranged. 



The family Textulariidae is apparently the most primitive, after the 

 Lituolidae. A number of the genera are wholly or in part composed of 

 species with arenaceous tests, which is in itself a primitive character in the 

 group. In many species both the microspheric and megalospheric forms 

 are known. In the microspheric form, which repeats most completely the 

 phylogenetic characters, a coiled early development succeeding the proloculum 

 is commonly found. This stage may be compared to the entire development 

 of such a genus as Haplophragmoides in the Lituolidae. 



Subfamily A. SriROPLECTiNAE Cuslnnaii. 



Test either coarsely arenaceous or ralcareous, or even hyaline, the early chambers 

 following the proloculum closely coiled, the later chambers biserial, occasionally tending 

 to become uniserial in the last developed chambers. 



This subfamily includes the single genus Spiroplecta Ehrb., which in its 

 developmental stages connects the Textulariidae with the Lituolidae. Its de- 

 velopment is primitive in that the stages are seen in both the microspheric 

 and megalospheric forms of the species, and are of comparatively long duration. 

 Cretaceous and post-Tertiary. 



Subfamily B. Textularinae Brady. 



Test typically biserial, early portion in microspheric form often with a few coiled 

 chambers, followed by biserial ones, later chambers varioicsly modified in different 

 genera, uniserial, broadly extended, etc. JFall either arenaceous or calcareous and 

 hyaline, perforate ; aperture single, or in a few cases, many present in a single 

 chamber. 



Textularia Defr. (Fig. 14, A). Test usually elongated, straight, tapering, 

 or turbinated. Chambers biserial, alternating and communicating with each 



