134 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
mural rim; it is an olocyst partially covered with a pleurocyst. The ovicell 
borders the mural rim in a very irregular fashion ; we are not absolutely certain 
that the opercular valve always closes the zooecia. Moreover, as we possess only 
a very small number of fragments, this species requires further examination. 
Occurrence. — Lower Jacksonian (Mooclys marl) : Jackson, Mississippi (very 
rare). 
Middle Jacksonian: Eutaw Springs, South Carolina (very rare); Rich Hill, 
51 miles southeast of Knoxville, Georgia (very rare) ; Wilmington, North Carolina 
(very rare). 
Cotypes. — Cat. Nos. 63902, 63903, U.S.N.M. 
MEMBRANIPORIDRA PACHYMURALIS, new species. 
Plate 28, figs. 14-17. 
Descnption. — The zoarium incrusts shells. The zooecia are slightly elongated, 
distinct, hexagonal; the mural rim is very wide on the margins and below, finely 
granular. The opesiiun is elongated, elliptical, fringed with a collar of granules 
radially arranged. The ovicell is much sunken, but placed above the distal septula; 
it is closed above by a globular, salient convexity, separated from the mural rim 
and formed of two calcareous layers. 
Measurements. — Opesia 
j ho= 0.35-0.40 mm. 
|Ze>=0.20 mm. 
„ . \Lz=0. 55-0.60 mm. 
Zooecia , „ . _ „ 
[Zs= 0.45-0.50 mm. 
Variations. — The zooecia are generally separated by a furrow of slight depth 
and sometimes filled up. The mural rim on account of its thickness is a true 
cryptocyst which renders this species very easy of determination. We are igno- 
rant of the use of the radially arranged granulations which fringe the opesium. 
No regenerated zooecia have been observed. The rather large distal septula 
becomes multiporous. 
Occurrence. — Middle Jacksonian (Castle Havne limestone) : Wilmington, 
North Carolina (rare). 
Holotype. — Cat. No. 63917, U.S.N.M. 
MEMBRANIPORIDRA TRIGEMMA, new species. 
Plate 25, figs.' 14, 15. 
The zoarium is unilamellar and creeps over algae. The zooecia are rather 
large, little elongated, ogival, distinct; the mural rim is thin, little prominent, 
curved, much enlarged at the base, finely granular. The opesium is elliptical or 
subcircular, finely denticulated. The ovicell is large, globular, salient, distinct 
from the mural rim, with a deeply embedded floor. 
M easurements. — Opesia 
j ho~ 0.46-0.50 mm. 
| lo= 0.36-0.40 mm. 
Zooecia 
\Lz— 0.60 mm. 
\lz= 0.55 mm. 
Affinities. — In general, in gemmation a zooecium may engender only two, 
of which the one that is deformed becomes primoserial. Here this gemmation is 
