NORTH AMERICAN EARLY TERTIARY BRYOZOA. 627 



The ovicell is hyperstomial, placed on the distal zooecium; it is never closed 

 by the operculum; its orifice is large; it is formed of two calcareous layers, of which 

 the external one is frequently incomplete and circumscribes a more or less large 

 frontal area. 



Variations.- In the interior of certain apertures there is a calcareous arched 

 lamella or indeed a, tooth when this lamella is incomplete. 



In the interior (fig. 2) the ancestrula is an ordinary zooecium; viewed from 

 the inner face it has the aspect of a circle perforated by three pores (fig. 5) sur- 

 rounded by a calcareous ring and by six hexagons perforated by three, four or five 

 pores. On the exterior it is surrounded by radicular zooeciules, as is the habit of 

 all the species attached to submarine bodies (figs. 7, 8). 



The zooecia are regularly cylindrical ; the internal surface is smaller than the 

 external surface; the discrepancy is filled by the zooeciules, which we call com- 

 pensation zooeciules; they are more or less numerous (fig. 3). 



On their inner face, near the ancestrula, there are some large avicularia with 

 bar; their mandible was semielliptical and transverse (figs. 4, 5). 



On the external face (fig. 6) there are large membraniporoid zooecia superposed 

 on the others and always situated near the center. Their function is unknown. 



The base of the zooecia is perforated; these pores are the extremities of the 

 long tubules which open also on the external face. These tubules must be intended 

 to give lightness to the zoarium. 



Occurrence. Claibornian (Gosport sand) : Claiborne, Alabama (very com- 

 mon) ; Gopher Hill, Tombigbee River, Alabama (common) ; one mile southwest 

 of Rockville, Clarke County. Alabama. 



Claibornian (Lisbon formation) : Wautubbee Hills, four miles south of Enter- 

 prise,. Clarke County, Mississippi (common). 



Claibornian (Cook Mountain formation) : Moseleys Ferry, Caldwell County, 

 Texas (very rare). 



Lower Jacksonian : Three and one-half miles southeast of Shell Bluff post office, 

 Georgia (rare). 



Lower Jacksonian: Jackson, Mississippi (very common). 



Plesiotypes.Csit. No. 62809, U.S.N.M. 



SCHIZORTHOSECOS GRANDIPOROSUM, new species. 



Plate 18, figs. 30-15. 



Description. The zoarium is cupuliform and little concave. The zooecia are 

 distinct exteriorly, tubular, terminated by a contracted peristomie. The apertura 

 is placed at the base, of the peristomie; it bears a rounded rimule; the peristomice 

 is oval. The peristomes are separated by some compensation zooeciules with irregu- 

 lar orifices. On their inner face the zooecia are indistinct; they each contain one 

 large and one small pore. At the base of each zooecium there are a dozen very 

 small pores. 



