NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
635 
1 Calvet, Contributions a l'histoire naturelle ties Bryozoaircs ectoproctes marins, p. 230. 
D x 100 
Fig. 196. — Structure of Hie tubes. 
A. Longitudinal section of Entalopliora 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 Plagioecia concreta new species, X 12, illustrating the spindle-shaped aspect of the 
tubes. C. Transverse thin section of a branch of Crisin dentieulata Lamarck, 1836; eat 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. B. 
Tangential thin section of the ectocyst of Crisia dentieulata Lamarck, 1836. Each of the pores 
corresponds to a spherular 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 ancl irregularly placed. 
The calcareous skeleton is exteriorly porous (fig. f 96 A, D). At each pore 
in the general cavity 1 there are corresponding spherular leucocytes (fig. 196 E). 
B x 1 2 
ect * 
