PLATE XI. 



Trochammina, Lituola, ValvuUna, and Acicidaria. 



Pig. 



1 — 10. — -Various forms of Trochammina, magnified 



50 diameters. 

 I .' — Trochammina squamata. 

 2. — Trochammina incerta. 

 3. — Trochammina charoides. 

 4. — Trochammina gordialis. 

 5. — Trochammina inflata. 



6 — 10. — Various forms of Trochammina irreyularis. 

 1 1 — 14. — Placopsiline forms of Lituola cenomana ; 



magnified 15 diameters. 

 15 — 26. — Various forms of ValvuUna; magnified 



15 diameters. 

 15. — Typical example of ValvuUna trianffularis as seen 



from its apex. 

 If). — Depressed variety of ValvuUna; the moutli of 



the same shell is shown in Fig. 23. 

 17, 18. — Clavuline varieties of ValvuUna. 



19, 25. — Bulimine varieties of ValvuUna. 



20, 26. — Mouths of other examples of the same. 



Fig. 



21, 24. — Large valvular mouths of semioval variety 



of ValvuUna. 

 22. — Portion of the shell of one of the outer chambers 

 of ValvuUna, showing the perforations in its 

 proper shelly layer in the part from which the 

 arenaceous incrustation has been most com- 

 pletely removed. 



27 — 31 Various forms of Acicidaria, showing the 



openings of the chambers, each of which, in 

 specimens whose natural surface has not been 

 destroyed by attrition, is surrounded by a lip, 

 as shown in Fig. 28 ; in Fig. 29, the attrition 

 has proceeded so far as to lay open the cavities 

 of the chambers ; magnified 20 diameters. 

 32. — Cylindrical specimen of Acicularia, of which the 

 chambers have been laid open by attrition, 

 and in which they present a honeycomb ar- 

 rangement ; magnified 40 diameters. 



