NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



253 



semblances of Eschara aegon D'Orbigny and E. atalantha D'Orbigny to Aspidos- 

 toma. Different species were described by Canu in 1904, 1908, and 1911. 



The known genera of this family are: 



Aspidostoma Hincks, 1881. 



Rhagasostoma Koschinsky, 1885. 



Euritina Canu, 1900. 



Odontiondla Canu and Bassler, 1917. 



Foraminella Levinsen, 1909. 



Cratcropora Levinsen, 1909. 



Labiopora Levinsen. 1909. 



FIG. 65. Family Aspidostomidae Canu, 1008. 



A-G. Aspidostoma giganteum Busk, 18S4. A. Several zooecia, two of them with ovicells, 

 X 23. B. A longitudinal section through two zooecia, X 23. C. A transverse section through two 

 y.ooecia. X 23. Uppermost a distal wall is seen and to the left of this the arched distal end of 

 the zooecium. Further down an intersected polypide tube is seen and on each side of this a 

 recess which extends to the basal wall. D. A transverse section through n zooecium, X 23. The 

 median projection of the zooecium is seen beneath the polypide tube. (A-D After Levinsen, 

 3909.) E. Avicularian mandible, X 85. F. Operculum, X 85. (E, F after Waters, 1SS8.) G. 

 Distal connections and lateral connections through the septulae, : 85. (After Waters, 

 1905.) 



Genus RHAGASOSTOMA Koschinsky, 1885. 



1885. Rhagasostoma KOSCHINSKY, Ein Beitrag zur Kenntnis der Bryozoenfauna der alterer 

 Tertiarschichten Bayerus, Paleontographica, vol. 32, p. 29. 



The ovicell is hyperstomial and opens above the opercular valve; it has no 

 lateral expansions (compressed process). The avicularia are interzooecial. 



Genotype. Rhagasostoma hcxagomnn Koschinsky, 1885. 



Range. Eocene-Miocene. 



The definition of this genus, established by Koschinsky in 1885. wa.s extended 

 by Canu in 1900 to all the species provided with opesial incision. The number of 



