NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
121 
Affinities. —The intensity of the calcification is remarkable in this species 
and gives to it an aspect very characteristic and difficult to figure. The large 
avicularium is triangular, the beak pointing upward; the pivot is almost always 
broken. The distal border of the apertura is often denticulated by the rupture 
of the hollow spines much wider than the peristome. In spite of its double pro¬ 
tective envelope the ovicell is often broken. The exterior aspect is absolutely 
unique. This species must have lived in a strong current. 
Occurrence.—Miocene (Duplin marl): Darlington Courthouse, South Carolina 
(rare). 
Holotype. —Cat. No. 68591, U.S.N.M. 
MICROPORELLA BIFOLIATA Ulrich and Bassler, 1904. 
Plate 20, figs. 7—11. 
1904. Microporella? bifoliata Ulrich and Bassler, Maryland Geological Survey, Miocene, p. 417, 
pi. 113, figs. 6-8. 
The original description is as follows: 
Zoarium erect, bifoliate, not known to branch. Zooecia subquadrate or hexagonal, arranged in 
regular longitudinal and diagonally intersecting series, four longitudinally and five diagonally in 2 
mm. Appearance of surface varying with age. In young examples the zooecia are more or less convex 
and separated, especially transversely, by an impressed line containing one or more rows of pores; 
the orifice is somewhat transverse and subovate with the proximal side straightened, the peristome 
but little elevated, the front sparsely punctated, the avicularia of which there is usually one to each 
zooecium placed some distance beneath and to one side of the orifice, rather large, subcircular and 
divided into two nearly equal parts by a thin partition. In old examples the oral part is sunken and 
the rest of the surface abundantly punctate, while the avicularia have been somewhat reduced in size. 
Immediately behind the orifice there is always a small (? peristomial) pore. Ovicells large, rather 
strongly convex, punctate. 
Measurements. —Apertura! 0.11 mm. Zooecia,, _ 
r [Za = 0.12mm. [lz = 0.25-0.35 mm. 
We have nothing to add to the original description except to call attention 
to the fact that the ascopore is crescent shaped. 
This species differ from Microporella ciliata Linnaeus, 1759, in the absence of 
frontal granules, in the presence of larger tremopores and in its nontransverse 
aperture which is almost as high as wide. The erect form of the zoarium is rather 
rare in the genus Microporella and it appears to form a good character for this 
species. Nevertheless we have observed bilamellar expansions in Microporella 
ciliata. 
Occurrence. —Miocene (Choptank formation): Cordova, Maryland (rare). 
Cotypes. —Cat. No. 68592, U.S.N.M. 
[ = 0.55 mm. 
MICROPORELLA FISSURIFERA, new species. 
Plate 19, figs. 12-13. 
Description. —The zoarium incrusts shells. The zooecia are distinct, separated 
by a deep furrow, elliptical, little elongated, wide; the frontal is convex and per¬ 
forated by a large number of tremopores. The apertura is semilunar, transverse; it 
is surrounded by a thin peristome bearing four large spines. The ascopore is placed 
12184—23—Bull. 125-9 
