NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
767 
The longitudinal section (fig. 18) shows us larger and less entangled tergo- 
pores than in Pleuronea alveolata; they are also longer and more oblique. 
Affinities. — When the tergopores are arranged in longitudinal series this species 
presents the aspect of Pleuronea -fibrosa ; but it is distinguished from it by its much 
larger orifice and the greater separation of the fascicles. 
It differs from Pleuronea alveolata, in the greater separation of the fascicles 
and in the different position of the ovicell, and from Idmonea reticulata Reuss, 
1869, in the very different form of the orifice of the tergopores. 
Occurrence. — Claibornian (Gosport sand) : One mile south of Rockville, 
Clarke County, Alabama (rare). 
Lower Jacksonian (Moodys marl): Jackson, Mississippi (very common). 
Middle Jacksonian : One-half mile southeast of Georgia Kaolin Company’s mine, 
Twiggs County, Georgia (rare) ; 12 miles southeast of Marshallville, Georgia 
(rare); Baldock, Barnwell County, South Carolina (very rare). 
Jacksonian (Zeuglodon zone) : Bluff on south side of Suck Creek, Clarke 
County, Mississippi ; Shubuta, Mississippi (common). 
Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles south of Jackson, 
Alabama (rare) ; Vicksburg, Mississippi (rare) ; Murder Creek, east of Castlebury, 
Conecuh County, Alabama (very rare). 
Geological distribution. — Helvetian of Italy (Neviani) ; Tortonian of Austria- 
Hungary (Manzoni) and Italy (Neviani) ; Astian of England (Busk). 
Plesiotypes. — Cat. Nos. 65266, 65267, U.S.N.M. 
PLEURONEA SUBPERTUSA, new species. 
Plate 113, tigs. 6-15. 
Description. — The zoarium is free, branched, with suborbieular section, 
idmoneiform. The fascicles are quite oblique, opposite, and reunite on the zoarial 
axis. The tubes are salient, with the maximum number of six to a fascicle; they 
are flat and are separated by a salient thread. The basal lamella bears tergopores, 
the diameter of which is perceptibly equal to that of the tubes. 
I Diameter of the peristomes 0.10 mm. 
easut ements. [Distance between the fascicles 0.20-0.28 mm. 
Variations . — The species is rarely well preserved; it must have frequented 
violent currents or agitated waters. The basal lamella with its tergopores is easily 
detached from the anterior portion of the zoarium (fig 10). 
The tergopores are deprived of polypide; their diameter is that of the tubes. 
They grow on the dorsal of the tubes in variable number; they diverge at first 
superiorly and then curve abruptly perpendicularly to the zoarial axis, thus form- 
ing a right angle (fig. 15). Their walls are thickened, a fact which is perfectly 
visible in tangential sections (fig. 12) ; they are orbicular in the interior and 
polygonal at the exterior. 
Each tergopore has only one point of tangency with each of the other tergo- 
pores which surround it. The interstices between the nonadjacent walls are rarely 
