CYCLOSTOMATOUS BRYOZOA CANU AND BASSLER 



41 



the same fragment of frond (figs. 2, 7); the tubes cease to be visible 

 and the peristomes are very salient (fig. 2) . The latter frequently 

 are less developed (figs. 3, 4, 6) and the superficial aspect is totally 

 different. In some very rare cases they become almost adjacent 

 (fig. 5.) 



The ovicell shown in Figure 3 is the typical and perfect form; it 

 is heart-shaped, transverse, convex, smooth, symmetrical, and its 



small oeciostome is placed in the median axis; but regularity and 

 symmetry disappear rather easily (fig. 6). The oeciostome meas- 

 ures 0.10 mm. and the oeciopore 0.06 mm. 



The zone of growth is short but very thick (figs. 2, 5). 



Structure. — In longitudinal section the tubes are long, club-shaped, 

 much expanded at their extremity, where, in consequence of the 

 closeness of the peristomes, they appear closed by pseudofacettes. 



