NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



635 



The calcareous skeleton is exteriorly porous (fig. 196 A, D). At each pore 

 in the general cavity 1 there are corresponding spherular leucocytes (fig. 196 E). 



4- 



A 



D xioo 

 FIG. 106. Structure of the tubes. 



A. Longitudinal section of Entalophora raripora D'Orbigny enlarged, showing that each tube 

 grows from the dorsal of the proximal tube. (After Beissel, 1865.) B. Tangential section of the 

 dorsal side of Plngioecia concreta new species, X 12, illustrating the spindle-shaped aspect of the 

 tubes. C. Transverse thin section of a branch of Crisia dcnticulata Lamarck, 1836; ect repre- 

 sents the ectocyst. (See text figure 229 for complete description.) D. Tangential thin sec- 

 tion, X 100, of the frontal of Filisparsa Ingens new species, illustrating the porous walls. E. 

 Tangential thin section of the ectocyst of Crisia dentifwJata Lamarck, 1836. Each of the pores 

 corresponds to a spberular leucocyte. (C, E after Calvet, 1900.) 



The pores serve therefore for respiration. The tubes communicate by septulae 

 (fig. 196 A), which are more or less numerous, very small and irregularly placed. 



1 Calvet. Contributions a 1'histoire naturelle des Bryozoaires ectoproctes marins, p. 239. 



