NORTH AMERICAN EARLY TERTIARY BRYOZOA. 287 



MEMBRANIPORELLA ULRICHI, new species. 



Plate 41, figs. 4, 5. 



Description. The zoarium is free, bilamellar, bush-like. The zooecia are 

 little distinct, joined together by their mural rim, thin, very elongated, lozenge- 

 shaped; the cribriform area is shallow, flat, and contains 10 to 12 very narrow trans- 

 verse slits; the axis of the suture of the costules is salient. The aperture is elon- 

 gated, semilimar; its proximal border is provided with a quite salient thorn-like 

 projection. The ovicell is large, embedded in the distal zooecia, salient, globular, 

 always closed by the operculum, and formed of two calcareous lamellae, of which the 

 outer one is porous. The two oral avicularia are large, fusiform, and prominent; 

 the pivot is indicated by two small, lateral teeth. 



=.ii. . 



Measurements. Aperture , . .. r Zooecia 



Ua=0.15 mm. 



Affinities. This fine species is very constant in all its characters. A tangential 

 thin section (fig. 5) shows that the costules are formed of rather large, scattered 

 olocystal elements, regularly placed. 



M embraniporella ulrichi differs from Menibraniporetto planula in its mural 

 rims, which join each other; in its much larger avicularia (Zv=0.25 mm.) ; in the 

 extreme thinness of the lumen (0.01 mm.), and in the sharpness of the proximal 

 border of the aperture. 



It can be distinguished from M embraniporella Itioculata by its small and non- 

 bifurcated oral prominence, by its much smaller and more numerous costules. by its 

 larger avicularia (Z-y=0.25 mm.) and by its much longer ovicells (hov 0.20 mm. 

 instead of 0.15 mm.). 



We dedicate this species to Dr. Edward O. Ulrich, whose brilliant work on 

 the Paleozoic bryozoa has a world-wide reputation, and who was among the first 

 to take up the serious study of the American Tertiary forms. 



Occurrence. Middle Jacksonian: near Lenuds Ferry, South Carolina (abun- 

 dant) ; Eutaw Springs, South Carolina (abundant) ; Wilmington. North Carolina 

 (rare). 



Ootypes.Cat. No. 61016, U.S.N.M. 



MEMBRANIPORHLLA BIOCULATA, new species. 



Plate 41, figs. 11-13. 



Description. The zoarium incrusts bryozoa. The zooecia are distinct, sep- 

 arated by a furrow, elongate, elliptical; the cribriform area is very convex, con- 

 taining five or six pairs of radial slits. The costules have a lumen pore at the loop. 

 The aperture is semilunar; the proximal edge has a large bifurcated mucro, the 

 branches of which frequently rejoin the oral avicularia, thus forming a new orifice 

 above the aperture; distal spines are sometimes present. The ovicell is prominent, 

 globular, smooth, little sunken in the distal zooecia, always closed by the operculum. 

 The two oral avicularia are salient, oval, the point at the top; the pivot is cal- 

 careous or simply indicated by two lateral denticles. 



