NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
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base. The cryptocyst is deep, smooth , and somewhat convex; the polypidian con- 
vexity is improminent and the opesiules somewhat linear. The ovicell is globular, 
salient, smooth, opening in a large orifice above the opercular valve. The avicularimn 
is interzooecial, smaller than the zooecium, fusiform, terminated by a small but wide 
canal ; its opesium is median and very small. 
Measurements . — Opesium 
f7m=0.10mm. 
1 ^<9=0.15 mm. 
Avicularimn 
\Lav= 0.40-0.50 mm. 
\lav=0R0 mm. 
Zooecium f Lz— 0.55-0.60 mm. 
(including opesiules) lfe=0.35-0.40 mm. 
Affinities.- — This species differs from Aechmella f Umar go in its hyperstomial 
ovicell. It may be distinguished from Rhagasostoma minusculum by its larger 
dimensions. Specimens from both the Jacksonian and Vicksburgian have been 
discovered. It appears to us that there were no essential differences between them, 
so we have united them under the same species. 
Occurrence. — Middle Jacksonian (Castle Hayne limestone) : Wilmington, North 
Carolina (very rare). 
Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles south of Jackson, 
Alabama (very rare). 
Cotypes. — Cat. Nos. 64000, 64001, U.S.N.M. 
RHAGASOSTOMA MINUSCULUM, new species. 
Plate 39, fig. 8. 
D ascription . — The zoarium incrusts bryozoa. The zooecia are very small , oval, 
distinct, separated by a furrow; the mural rim is prominent, slightly thickened, 
enlarged at the base, complete. The cryptocyst is deep, smooth, flat ; the polypidian 
convexity is improminent; the opesiules are rounded incisions. The ovicell is 
globular and prominent. The avicularimn is interzooecial, elongated, fusiform, ter- 
minated by a very short but wide canal. 
M easurements.- 
. \ho~ 0.07 mm. 
-Opesium 7 
1 U 0 =O.lOmm. 
Zooecium [Zs=0.30-0.35 mm. 
(including opesiules) lfe=0.24— 0.28 mm. 
Avicularimn 
I Lav=0R0 mm. 
\lav=0.W mm. 
Affinities. — This is one of the smallest bryozoans known. It is difficult to con- 
ceive how such a small structure could contain tentacles, pharynx, stomach, intes- 
tines, muscles, and ovaries and lodge a creature much more perfected than an oyster 
or a Tridacne. 
Occurrence . — Middle Jacksonian: Wilmington, North Carolina (very rare) ; 
Eutaw Springs, South Carolina (very rare). 
Holotype . — Cat. No. 64002, U.S.N.M. 
