154 PROCEEDINGS OP THE NATION" AL MUSEUM vol.72 



The seat of this hydrostatic apparatus is the interior face of the 

 colonies. This is variable according to the form and size. The 

 zooecia appear hexagonal, especially on specimens with the ectocyst; 

 on others the character is little visible, and more often the cells are 

 grouped in radial series. Each hexagon bears small, hollow, very 

 UTegular elevations and either a very small avicularium or a large 

 avicularium identical with those of the superior cellular face. The 

 large avicularia are arranged in widely spaced circular series. This 

 character is specific and permits one to easily distinguish the species 

 in the fossil forms in spite of the great irregularity of the elevations. 

 We have already shown that in many other genera of bryozoa these 

 elevations are really hydrostatic, and we have here still another proof. 

 The physiologic function of the avicularium is here impossible to 

 establish. The small specimens are deprived of them and certain 

 species do not have them at all. The most reasonable hypothesis 

 is that they are organs of defense against parasitism, for on the 50 

 specimens observed none of them bears parasitic colonies. 



The longitudinal section shows that the cells are simple, erect hex- 

 agons with bases somewhat convex. This is a more simple architec- 

 ture than that of Cones cJiarellina and of Flahellopora, in which the 

 bases are hexagonal pyramids. 



The aperture is large, provided with two cardelles, and is placed 

 at the center of the superior base. It is surrounded by a very thick 

 peristome and covered also by the small very irregular tuberosities, 

 characteristic of the genus. There is therefore a zooecial surface vis- 

 ible, contrary to that observed in other genera of the family. The 

 peristome always bears to the right or to the left an elliptical avicu- 

 larium more or less salient, the pivot of which is indicated by two 

 lateral denticles.' Smitt's figure is incorrect, for the avicularium 

 appears here as interzooecial, although it is always peristomial and is 

 not visible at the interior. 



The ovicelled zooecia are wider than the adjacent zooecia; their 

 aperture is also somewhat larger. The visible zooecial length is 

 double, for they are formed of two cavities separated by a vertical 

 partition. The proximal cavity is an ordinary zooecium, while the 

 very large distal cavity is uniquely destined for the development of 

 the embryos. The operculum closes the ovicell but it may fall and 

 become supported on the separating partition, opening thus the ovicell 

 for the escape of the larvae. This is really a kind of endozooecial 

 ovicell, for the distal cavity occupies the place of another zooecium. 

 This is another generic character that is not observed in other genera 

 which have hyperstomial ovicells more or less embedded in the distal 

 zooecia. 



The operculum is much chitinized and bordered with a more or 

 less broad and thick sclerite. It bears two broad linear attachments 



