NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



643 



The tergopores have so far been observed only in the genera Mesonea and 

 Pleuronea. 



Firmatopores. The firmatopores (=canal of reenforcement of Pergens) are 

 longitudinal, cylindrical, capillary tubes on the dorsal of the zoarium. They 

 arise on the basal lamella at all heights and are directed toward the base in the 

 opposite direction to the zooecia which are ascending; they form by their opening 

 on the substratum, the basal system of fixation of the zoarium (fig. 203). 



FIG. 204. Nematopores. 



Longitudinal thin section, X 

 25, of Diplodcsmopora oppo- 

 sita new genus and species 

 from the Coniacian at Tours, 

 Prance, showing zooecial tubes 

 to right and nematopores to 

 left. 



A x25 



B x12 



FIG. 205. Dactylethrae. 



A. Longitudinal thin section of Erkosonca 

 scmota new species, X 25, showing dactyle- 

 thrae (to right) and zooecial tubes. B. Dorsal 

 of the same species, X 12, illustrating dactyl e- 

 thrae closed by a lamella. C. Longitudinal 

 thin section of dausa hetcropom D'Orbigny, 

 showing dactylethrae (to right) and zooecial 

 tubes. 



Nematopores. The nematopores are inferior and opposite ramifications of 

 the oriented tubes; they are always rectilinear and their orifice is oblique. Their 

 walls are thin or thick, but always adjacent. They are sometimes closed by a 

 calcareous cpitheca (fig. 204). They are distinguished from firmatopores, which 

 have the same threadlike aspect, in their ascending and not descending arrange- 

 ment. 



