NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



69 



We have avoided the use of these archaic terms in our descriptions save 

 Eschara, Lunulites, and Vincularia. 



The causes of zoarial variations are unknown. 



The free zoaria very seldom remain intact in fossilization and we most always 

 find them in the state of minute fragments. When the lattor are very numerous it 

 is always interesting to attempt their restoration. Those which we have made 



Ex50 



3 x20 



FIG. 15. Structure of the vestibular arch, etc. 



A. Membrendoecium rectum, new species. X 20. Calcified zooecia. 



B. Hincksina vicksburgica, new species. X 20. Opesium not completely covered by calci- 

 fication. 



C. D. Harmeria diaphana MacGillivray. 1879. C. The distal half of a zooecium, the frontal 

 wall of which has been removed, so that the highly developed vestibular arch may be seen and 

 the rods by which it is connected with the lateral walls, X 55. D. The distal half of a zooecium, 

 seen from the "basal surface after removal of the basal wall. The basal wall of the vestibular 

 arch is seen, X 55. ( After Levinsen, 1909.) 



E. Vestibular arch of MticroncUa peartii Johnston, 1847, X 50. ( After Busk, ]S54.) 



F. Diatoms and radiolaria found in the digestive apparatus of Clia/icrin x/iinoftu Qnoy and 

 Caimarrt, 1824. (After Jullien, 1S8S.) 



belong to species branching in a single plane and were relatively esuy. AVe yet do 

 not know how to restore the bushy zoaria. 



Habitat. The bryozoa live first, in deep water; second, in waters always 

 clear and limpid; and, third, in waters constantly agitated superficially by tempests 

 and deeply stirred by currents. (D'Or'nigny. 1S50.) 



