NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
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Fig. 25.—Genus Inversiula Jullien, 1888. 
A. Inversiula nutrix Jullien, 1888. Zooecium. (After Jullien, 1888.) 
B-F. Inversiula inversa Waters, 1889. B. Zooecia, X 25.' C. Decalcified zooecia, X 50. Distinct 
tubes occupy the place of the grooves. The interior membrane of the zooecial wall is not perforated by 
the stellate pores. A stellate pore X 250 is represented at a. D. Three stages of growth, X 50. There 
are deep grooves between the stellate pores. (B-D, after Waters, 1889.) E. Structure of the stellate 
pores, X 200. (After Levinsen, 1909.) F. Operculum, X 250. (After Waters, 1887.) 
Genus INVERSIULA Jullien, 1888. 
1888. Inversiula Jullien, Mission scientifique du Cap Horn. 1882-83, VI, Zoologie, Bryozoaires, 
p. 41. 
No ovicell. The frontal is a tremocyst with stellate pores. The aperture is 
elliptical and transverse. The convexity of the ascopore is turned toward the 
aperture. Avicularia are present. No spines. 
Genotype.—Inversiula nutrix Jullien, 1888. 
Range. —Miocene-Recent. 
The known species of this genus are: 
Inversiula nutrix Jullien, 1888. 
Inversiula ( Microporella) inversa Waters, 1889. 
Inversiula ( Microporella) airensis Maplestone, 1910. 
Inversiula ( Microporella) guadricornis Maplestone, 1910. 
Group 3. HIPPOPORAE Canu and Bassler, 1917. 
Genus HIPPOPORINA Neviani, 1895. 
(For description see Bulletin 106, U. S. National Museum, p. 374.) 
HIPPOPOKINA PUSILLA, new species. 
Plate 45, figs. 8, 9. 
Description. —The zoarium incrusts sponges and corals. The zooecia are dis¬ 
tinct, separated by a furrow, small, elongate, elliptical; the frontal is an absolutely 
smooth olocyst. The apertura is very small, surrounded by a thick peristome which 
