122 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
We take pleasure in dedicating this species to Mr. E. N. Lowe, State geologist 
of Mississippi, who has spared no efforts in supplying us with material for study. 
Occurrence . — Vicksburgian (Bryam marl) : Vicksburg, Mississippi (rare). 
Holotype. — Cat. No. 64233, U.S.N.M. 
MEMBRENDOECIUM RECTUM, new species. 
Plate 13, figs, 1-8. 
The zoarium incrusts other bryozoa and pebbles. The zooecia are elongate, 
distinct, oval ; the mural rim is salient, smooth, a little widened on the margins, 
very much widened at the base, with five distal dietellae. The opesium is oval, 
entire. The ovicell is endozooecial and is a small, smooth, distal convexity. The 
avicularia are small, straight , salient, and elliptical. The ancestrula is a very 
small, closed zooecium. 
Measurements . — Opesia 
Ao= 0.14-0. 16 mm. 
lo= 0.10 mm. 
Zooecia 
|Zs=0.32-0.40 mm. 
\lz= 0.20-0.24 mm. 
Variations . — Specimens of this species assume a little different aspect according 
to their geologic horizon, although not enough to make it possible to establish true 
specific differences. Very frequently in the Claibornian and Jacksonian the zooecial 
length does not surpass 0.22-0.24 mm. However, these variations depend chiefly 
on the presence or absence of a small gymnocyst. 
Around the ancestrula there is an important group of closed zooecia perforated 
with a circular pore and bearing clistally. as is usual the imprint of the opercular 
valve, which we must therefore suppose to have been thickened on its edges. We 
have observed some regenerated zooecia with double mural rims. 
A-ffinities . — This species differs from M embrendoecium duplex in the widening 
of the mural rim at the base and in that the zooecia do not become confluent. It 
differs from M. pyriforme in its smaller micrometer dimensions and the almost 
general absence of a gymnocyst. 
Occurrence . — Lower Jacksonian: 34 miles southeast of Shell Bluff post office, 
Georgia (rare). 
Middle Jacksonian: Wilmington, North Carolina (very rare); 18 miles west 
of Wrightsville, Hawkins County, Georgia (rare) ; \ mile southeast of Georgia 
Kaolin Company Mine, Twiggs County, Georgia (rare) ; 17 miles northeast of 
Hawkinsville, Georgia (rare). 
Upper Jacksonian (Ocala limestone), Chipola River, east of Marianna, Jackson 
County, Florida (rare). 
Vicksburgian (Byram marl) : Byram, Misrissippi (common). 
Vicksburgian (“Chimney rock” of Marianna limestone) : One mile north of 
Monroeville, Alabama (common) ; near Claiborne, Monroe County, Alabama (rare). 
Vicksburgian (Glendon member of Marianna limestone) : West bank of Cone- 
cuh River, 1 mile below mouth of Sepulga River, Escambia County, Alabama (very 
rare). 
Cotypes. — Cat. Nos. 63842, 63965, U.S.N.M. 
