NORTH AMERICAN EARLY TERTIARY BRYOZOA. 787 



FIG. 1253. Idmiilrvnca, new genus. 



A-L. Idmidronea (Iflmonea) coronopus Defrance, 1822. A. Zoaria, natural size, from 

 various localities in the Lutetian of France. B. Zoarium, X 6, with layer of firmatopores form- 

 ing many columns (on rocks). C. Specimen, X 6, with a small basal plate of Hrrnatopores (in- 

 crusting shells), bearing a branch without firmatopores. D. A concave base of flrmatopores, X 6, 

 attached to an alga. E. A large base, X 12, without firmatopores. The ancestrular zooecium is 

 visible. F. A small base, X 12, without firmatopores. The ancestrular zooecium is visible. 

 G. The same specimen, X 25, showing absence of firmatopores. H. An example. X 6, showing 

 that the layer of firmatopores is separable. I. Specimen, X 12, showing that there are 

 many layers of firmatopores. J. The firmatopores occur at the bottom of sulci, X 12. K. Longi- 

 tudinal section in a thick zoarium through the axis of the fascicles, X 25. The basal lamella 

 <BB) is visible. The firmatopores are the cylindrical tubes growing on the basal lamella but 

 directed toward the base while the polypidian tubes are ascending. L. Longitudinal section, 

 X 25, in the thick zoarium taken between the fascicles and in the axis of a bifurcation. The 

 tinsal lamella (KB) is visible. M. Thin section in the base of a zoarium, X 25. 



