NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
253 
semblances of Eschara aegon D’Orbignv and E. atalarCtha D’Orbigny to Aspidos- 
toma. Different species were described by Canu in 190d, 1908, and 1911. 
The known genera of this family are : — ■ 
Aspklostoma Hincks, 1881. 
Rhagasostoma Koschinsky, 1885. 
Euritina Canu, 1900. 
0 dontionella Canu and Bassler, 1917. 
F ' oraminella Levinsen, 1909. 
Crateropora Levinsen, 1909. 
Labiopora Levinsen, 1909. 
Fig. 65. — Family Aspidostomidae Canu, 190S. 
A-G. Aspidostoma giganteum Busk, 1884. 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 
zooecia, 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 a zooecium, X 23. The 
median projection of the zooecium is seen beneath the polypide tube. (A-D After Levinsen, 
1909.) E. Avicularian mandible, X 85. F. Operculum, X 85. (E, F after Waters, 1888.) G. 
Distal connections and lateral connections through the septulae, X 85. (After Waters, 
1905.) 
Genus RHAGASOSTOMA Koschinsky, 1885. 
1885. Rhagasostoma Koschinsky, Ein Beitrag zur Kenntnis der Bryozoenfauna der alterer 
Tertiarschichten Bayerns, 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 hexagonum Koschinsky, 1885. 
Range. — Eocene-Miocene. 
The definition of this genus, established by Koschinsky in 1885, was extended 
by Canu in 1900 to all the species provided with opesial incision. The number of 
