NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
259 
either side connected with the lateral wall by a vertical calcareous lamina; multi- 
porous septulae. 
Genotype. — Labiopora crenulata Levinsen, 1909. 
Genus CRATEROPORA Levinsen, 1909. 
1909. Grateropora Levinsen, Morphological and systematic studies on the Cheilostomatous 
Bryozoa, p. 171. 
No ovicell; distinct raised margins; frontal wall of polypide-tube not quad- 
rangular and not surrounded by projecting flanges. Polypide-tube not bilabiate, 
with an expanded distal margin, not connected with the lateral walls by vertical cal- 
careous laminae; uniporous septulae. (Levinsen, 1909.) 
Genotype. — Grateropora falcata Levinsen. 1909. 
Aspidostoma flammulum Canu, 1908, of the Pata- 
gonian of Argentina may perhaps belong to this genus, 
although it bears ovicells. 
Family STEGANOPORELLIDAE Levinsen, 1909. 
Bibliography (Anatomical). — 1900. Harmer, A revision of the 
genus Steganoporella, Quarterly Journal Microscopical Science, 
vol. 43, pp. 225-295, pi. 12, 13. — 1902. Harmer, On the Mor- 
phology of the Cheilostomata, Quarterly Journal of Microscopi- 
cal Science, p. 317, pi. 18, figs. 64. 65, 66. — 1909. Levinsen, 
Morphological and systematic studies on the Cheilostomatous 
Bryozoa, p. 167, pi. 6, figs. 2-7. — 1913. Waters, Bryozoa from 
Zanzibar, Proceedings of the Zoological Society of London, p. 
498, pi. 72, figs. 12-20. 
The zooecium is divided into two chambers. The 
proximal chamber contains the polypide and the ovaries ; 
it is terminated by an ascending tube, the polypide 
tube, in which the tentacles are lodged when the polypide is retracted. The upper 
chamber contains the parietal and opercular muscles. The retractor muscles of the 
polypide are attached in one of the lower angles of the zooecium, which causes the 
general assymetry of the zooecium. No ovicells, no avicularia. Generally two 
forms of zooecia: a and B. The two opesiules are generally not separated from 
the aperture of the zooecium. The operculum, which is sometimes bounded by a 
ehitinous sclerite proximally, sometimes continued immediately into the frontal 
membrane, is, as a rule, very large, and then suspended by strong hinge-teeth. 
The structure in this family is remarkable and of great interest. The figures 
that are reproduced permit the reader to easily comprehend its details, despite the 
complexity of the terminology. The two known genera are Steganoporella Smitt, 
1873, and Siphonoporella Hincks, 1880. 
Genus STEGANOPORELLA Smitt, 1873. 
1873. Steganoporella Smitt, Floridan Bryozoa, Kongl. Svenska Vetinskaps-Akademiens 
Handlingar, vol. 11, No. 4, p. 15. 
The whole of the calcified part of the frontal area lying proximally to the 
aperture is a depressed cryptocyst ; the aperture of the zooecium is surrounded 
Fig. 70. — Genus Grateropora 
Levinsen, 1909. 
Crateropora falcata Levin- 
sen, 1909. Zooecia, X 23. (Af- 
ter Levinsen, 1909). 
