NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
491 
Affinities. — This species differs from Porella abdita in its distinct zooecia and 
in its zoarium creeping oi'er algae and not bilamellar. 
In its exterior aspect and in the nature of its zoarium it may be easily con- 
founded with Cyclicopora spongiopsis De Gregorio, 1882. It differs from it in the 
regular and constant presence of the median avicularium. 
Occurrence. — Vicksburgian (Marianna limestone) : West Bank Conecuh River, 
Escambia County, Alabama (common) ; Murder Creek, east of Castlebury, Conecuh 
County, Alabama (common) ; Claiborne, Monroe County, Alabama (common). 
Cotypes . — Cat. No. 64308, U.S.N.M. 
PORELLA CYLINDRICA, new species. 
Plate 94. figs. 14-17. 
Description . — The zoarium is free, cylindrical , bifurcated, formed by four 
to six longitudinal rows of zooecia. The zooecia are distinct, elongated, separated 
by a salient thread ; the frontal is somewhat convex and is formed of a thick tremo- 
cyst with large tubules. The apertura is deep and partially hidden by the median 
avicularium; it has no peristome. The median avicularium is enormous, very 
salient, very straight with an orifice turned toward the side of the apertura. 
M easurements. — Apertura 
r ha= ? mm. 
( Z«=0.11 mm. 
Zooecia- 
Lz—0. 85 mm. 
fe=0.40mm. 
Affinities.-— The vincularian form of its zoarium clearly distinguishes this 
species from the species with large median avicularium, such as Porella denti- 
culifera , Porella jacksonica , Porella pungens, and Porella unguiculata. 
Occurrence. — Vicksburgian (“ Chimney rock ” of Marianna limestone) : One 
mile north of Monroeville, Alabama (common). 
Cotypes . — Cat. No. 64304, U.S.N.M. 
PORELLA ERECTA. new species. 
Plate 93. figs. 17-20. 
Description . — The zoarium is free, bilamellar, formed of two lamellae, back 
to back, and inseparable; the fronds are narrow and bifurcated. 
The zooecia are distinct, long, tubular; the frontal is convex and formed 
of a tubular tremocyst placed on a thin olocyst with small pores. The apertura 
is semilunar, oblique, buried, by the umbo when the latter is entire; it has no 
peristome. The ovicell is globular, salient, with a finely porous area; it is hvper- 
stomial and opens into the peristomie. The median avicularium forms a very salient 
umbo little oblique above the aperture, almost erect , very thin, and very fragile at 
the extremity. 
Measurements. — Peristomice 
\hpe—0.1d> mm. 
{lpe=0.l§ mm. 
Zooecia 
Zs=0. 70 mm. 
73=0.44 mm. 
Apertura [ 7m=0.08 mm. 
(interior) Ua=0.10 mm. 
