NORTH AMERICAN EAI5LV 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 opSrculum. are present. 



MEMBRAN1PORELLA MODESTA Ulrich, 1901. 



Plate 1, figs. 22-25. 

 1901. CrilriUnn iiinilmtn. 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 Membraniporella; 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). 



s.Crt.. No. 63781, U.S.N.M. 



MEMBRAMPORELLA CRASSULA Ulrich, 1901. 



Plate 1, fig. 26. 

 1901. Cribrilina crassula ULRICH, Maryland Geological Survey, Eocene, p. 21S, 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). 



