NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
35 
SECTION II. MEMBRANIPORAE WITH ENDOZOOECIAL OVICELL. 
Genus VIBRACELLINA Canu and Bassler, 1917. 
(For description see Bulletin 106, U. S. National Museum, p. 110.) 
VIBRACELLINA PUSILLA, new species. 
Plate 10, figs. 4, 5. 
Description. —The zoarium incrusts shells. The zooecia are small, oval, a little 
elongated, distinct, separated by a deep furrow; the mural rim is thin, rounded, 
salient, much enlarged at the base into a concave cryptocyst. The opesium is 
anterior, oval, regular. The ovicell is very small and endozooecial. The vibracula 
are small, salient, elliptical, auricular. 
,, , „ \ho = 0.14-0.16 mm. „ . 1 X 2 = 0.30 mm. 
Measurements .—Opesia 7 . „ Zooecia 7 _ ., 
F [7o = 0 . 10 mm. [ 72 = 0.14 mm. 
Affinities. —According to the rule in this genus, the ancestrular zooecia are 
smaller and frequently calcified. The ancestrula engenders five normal zooecia 
and three vibracular ones. In the proximal portion of the zooecia there is often a 
very short gymnocyst. 
This species differs from Membrendoecium rectum Canu and Bassler, 1920, from 
the Yicksburgian in its slightly smaller dimensions, its concave and not flat crypto¬ 
cyst and in its nonsalient mural rim. 
Occurrence. —Pliocene (Caloosahatchee marl): Shell Creek, De Soto County, 
Florida (very rare). Miocene (Duplin marl): Natural well, 2 miles southwest of 
Magnolia, North Carolina (rare). 
Cotypes. —Cat. Nos. 68435, 68436, U.S.N.M. 
VIBRACELLINA SIMPLEX, new species. 
Plate 10, figs. 6, 7. 
Description. —The zoarium incrusts shells. The zooecia are distinct, separated 
by a furrow, elongated, pyriform; the gymnocyst is smooth, convex, rather short; 
the termen is sharp. The opesium is oval, the point above. The ovicell is very 
small and endozooecial. The vibracula are rare, very small, auriculated. The 
ancestrula is calcified and presents a small semilunar aperture. 
^ |7to = 0 . 20 mm. ^ . [Lz = 0.35-0.40 mm. 
Measurements.- 
P eSia [ 7 o = 0.13-0.15 mm. -^ooeciaj ^ = q 25 mm. 
Structure .—The rarety of vibracula give to this species an aspect of great 
simplicity. The heterozooecia appear to be zooecia in which the development has 
been arrested by adjacent zooecia. The ancestrula and three ancestrular zooecia 
are calcified. The hexagonal symmetry in the arrangement of the ancestral zooecia 
is remarkable. Nevertheless, there are really only five zooecia issuing from the 
ancestrula according to the rule, and no vibracula. We have observed calcified 
zooecia and also regenerated zooecia in vicinity of the ancestrula. 
This species differs from Vibracellina pusilla in its larger micrometric dimen¬ 
sions and in the very great rarity of the vibracula. 
Occurrence .—Miocene (Choctowliatchee marl): Jackson Bluff, Ocklocknee River, 
25 miles southwest of Tallahassee, Florida (very rare). Miocene (Duplin marl): 
Natural well, 2 miles southwest of Magnolia, North Carolina (rare). 
Cotypes.— Cat, Nos. 68437, 68438, U.S.N.M. 
