NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
285 
Levinsen believed that this genus was very close to Callopora Gray, 1848, and 
that it could well be classified in the same family. But the larva is that of the 
Ascophora, although it is true that Barrois’s determination of the larva has never 
been verified, and that we have no information on the anatomy or larva of species 
of Callopora. Therefore, while awaiting more information, we must be content 
with a classification which, if it is not natural, is at least very convenient. 
The intervening slits are often accompanied by lacunae, as in the other genera 
of this group. The presence of the latter is therefore not an exclusive character 
if the other important characters, absence of lumen pores, and the ovicell always 
closed by the operculum, are present. 
MEMBRANIPORELLA MODESTA Ulrich, 1901. 
Plate 1, figs. 22-25. 
1901. Cribrilina modesta, Ulrich, Maryland Geological Survey, Eocene, p. 218, pi. 60, fig. 14. 
Original description . — ■“ Zoarium forming a delicate parasitic patch upon for- 
eign bodies. Zooecia ovate, not very regularly arranged, about 0.4 mm. in length 
and 0.28 mm. wide, bordered by a thin rim. Front wall gently convex, usually 
with six (five to seven) radiating and transverse furrows, or triangular space, 
including five or six similar pores placed in obscure transverse furrows. Apertures 
rounded, prominent, oblique, the posterior edge highest and often thickened in its 
central portion. Small avicularian cells occur near or attached to one part or 
another of the apertural rim of most zooecia, generally one to each, rarely two. 
Ooecia cucullate, moderately arched.” 
This is a true M embraniporella ; the slits are wide and complete. The lumen 
is often visible. The ovicell is embedded in the distal zooecia and its orifice is 
lower than the labial mucro. 
Occurrence . — Lowest Eocene (Bryozoan bed at base of Aquia formation) : 
Upper Marlboro, Maryland (rare). 
Plesiotypes. — Cat. No. 63781, U.S.N.M. 
MEMBRANIPORELLA CRASSULA Ulrich, 1901. 
Plate 1, fig. 26. 
1901. Cribrilina crassula Ulrich, Maryland Geological Survey, Eocene, p. 218, pi. 60, fig. 14. 
Original description . — “ Zoarium encrusting. Zooecia oblong, quadrate, or 
hexagonal, irregularly arranged, with a heavy, strongly elevated margin, clithridate 
in outline. Front wall with a narrow raised ridge running down its center, and 
five or six transverse and radiating rows of minute punctures lying in furrows. 
Apertures rounded or subovate, the outline often less curved on the posterior side 
than elsewhere. Avicularian cells small, raised, variously distributed, sometimes 
one or two and three to a zooecium; or a cell may have none at all. Ooecia un- 
known. Zooecia 0.5 to 0.6 mm. in length. 0.25 to 0.30 mm. wide; about seven in 
4 mm. measuring lengthwise.” 
Occurrence . — Lowest Eocene (Bryozoan bed at base of Aquia formation) : 
Upper Marlboro, Maryland (rare). 
