NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
39 
SECTION III. OVICELL HYPERSTOMIAL ALWAYS CLOSED BY THE OPERCULUM. 
Genus MEMBRANIPORIDRA Canu and Bassler, 1917. 
(For description, see Bulletin 106, U. S. National Museum, p. 133.) 
MEMBRANIPORIDRA PARCA, new species. 
Plate 12, fig. 7. 
Description. —The zoarium incrusts shells. The zooecia are distinct, separated 
by a deep furrow, regularly elliptical; the frontal is formed of a convex gymnocyst 
principally developed in the inferior part of the zooecium. The opesium is regularly 
elliptical and bears a distal indentation in which the operculum is placed. The 
ovicell is convex, smooth, transverse, placed on the gymnocyst of the distal zooecium ; 
it is always closed by the operculum. 
,, , ~ \ho = 0.30 mm. „ . [Zto = 0.50 mm. 
Measurements .—Opesia 7 . Zooecia 7 . 
1 to = 0.22 mm. to = 0.30 mm. 
Variations. —It is very difficult to interpret the operation of the operculum 
on the fossils. Here the ovicell is indeed separated from the opesium by the mural 
rim, but the superior indentation of the opesium which corresponds to the opercu¬ 
lum is of exactly the same form as the orifice of the ovicell. It is therefore very 
probable that our generic assignment is exact. 
This species rests directly upon the shell and does not secrete a calcareous 
dorsal. This economy of calcite is rather rare in the strata which are not exclusively 
arenaceous. 
Occurrence. —Miocene (Choctowhatchee marl): Jackson Bluff, Ocklocknee 
River, 25 miles southwest of Tallahassee, Florida (very rare). 
Holotype. —Cat. No. 68447, U.S.N.M. 
DIVISION IV. OVICELL NEVER CLOSED BY THE OPERCULUM. 
Genus ALDERINA Norman, 1903. 
(For description, see Bulletin 106, U. S. National Museum, p. 140.) 
ALDERINA CESTICELLA, new species. 
Plate 12, figs. 4, 5. 
Description. —The zoarium incrusts oysters. The zooecia are distinct, elon¬ 
gated, oval, separated by a deep furrow, ornamented by a short gymnocyst; the 
mural rim is thin; enlarged behind in the form of a cryptocyst, rounded, salient, 
garnished with six to eight large distal spines; the opesium is anterior, oval, sur¬ 
rounded by a salient and finely wrinkled collar. The ovicell is large, salient, 
globular, hemispherical, bearing a large, inferior collar, transverse and linear. The 
ancestrula bears an opesial sinus. 
,, „ . (ho = 0.20-0.25 mm. „ . \Lz = 0.40-0.50 mm. 
Measurements. Opesia| _ 0 , 5_ 0 2 2 mm . Zooecla | fe = 0 .25-0.30 mm. 
Affinities. —This species is irregular in its micrometric measurements, but the 
zooecial form remains always pyriform. The ancestrula is quite remarkable. It 
is elliptical and deprived of spines. It engenders two large and three small zooecia. 
Its opesium bears a deep sinus, the significance of which is unknown. The marginal 
