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.Q-Ai. No. 64233, U.S.N.M. 



MEMBRENDOECIUM RECTUM, new species. 



Plate 13, figs. 1-S. 



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. . [Zs=0.32-0.40 mm. 

 7 Aooecia 7 



Zo=0.10 mm. (73=0.20-0.24 mm. 



Variation.?. 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 distally. 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. 



Affinities. This species differs from M enibrendoecium 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, Xorth Carolina (very rare); IS 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). 



Yirksburgian (Byram marl) : Byram, Misrissippi (common). 



Vicksburgian ("'Chimney rock" of Marianna limestone) : One mile north of 

 Monrooville, Alabama (common) : near Claiborne, Monroe County, Alabama (rare). 



Vicksburgian (Glendon member of Marianna limestone) : West bank of Cone- 

 ,nih River, 1 mile below mouth of Sepulga River. Escambia County, Alabama (very 

 rare) . 



Cotypes.C^i. Nos. 63842, 63965, U.S.N.M. 



