636 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



These septulae serve as in the Cheilostomata. for the passage of the mesenchyma- 

 tous fibers. 



A x16 



Cx16 Dx60 



FIG. 197. Structure of the cylindrical tubes. 



A. Longitudinal thin section, X 16, of a massive species Ceriopora vesicutosa new species. 

 The walls are vesicular throughout their course. B. Transverse thin section, X 16, of Tretocy- 

 cloecia dicliotoma Reuss from the Helvetian of France. The tubes are of the same size at both 

 the center and circumference. C. Longitudinal thin section of a ramose species Tretocycloecia 

 K-lii-iiliita. new species, X 16. The interzooecial spaces are vesicular only at the extremity of the 

 tubes. L). Portion of longitudinal thin section, X 60, of Heteropora constanti D'Orbigny, show- 

 ing the great size sometimes attained by the vesicles. 



Cylindrical tubes or trepostomatous-like Cyclostomata. In this division the 

 inferior part of the tube is developed, but this part is very short. These tubes 



