EARLY TERTIARY CHEILOSTOME BRYOZOA. 21 



MEMBRANIPORIDRA, new genus. 



The operculum always closes the ovicell. No dietellae. No avicu- 

 laria. One large distal septula ; two pairs of lateral septulae. 



Genotype. — M emhi'aniporidra jyorrecta^ new^ species. 



The ovicell is deeply excavated in the distal zooecium. It is only 

 by dissection that we are able to prove by the continuity of the mural 

 rim, although very thin distally, that the ovicell is indeed hyper- 

 stomial. The mural rim is ahvays enlarged at the base and finely 

 granular. 



This genus differs from Alderina Norman, 1903 not only in the 

 closure of the ovicell by the opercular valve but also in the absence 

 of dietellae. 



MEMBRANIPORIDRA PORRECTA, new species. 



Plate 2, fig. 5. 

 The zoarium is free, follicular, formed of two very thin leaves, 

 growing back to back and easily separable. The zooecia are large, 

 elongate, distinct, oval, with a proximal, convex gymnocyst; the 

 mural rim is very thin, salient, curved. The opesium is large, ellip- 

 tical, entire. The ovicell is globular, little elevated, ornamented with 

 a frontal callosity ; it is deeply embedded. A distal septula and two 

 lateral septulae and two distal impressions are present. 



,, , r\ • \ ho=0.75 mm. „ . f Zs=0.95 mm. 



Measurements. — Opesia , ^ „^ Zocecia , ^ „„ 



^ [ Zo— 0.30 mm. [ 72=0.38 mm. 



Occurrence. — Middle Jacksonian: Wilmington, North Carolina 



(common). 



Baldock, Barnwell County, South Carolina (rare). 



Tijpe.—Csit. No. 62578, U.S.N.M. 



SECTION IV. OVICELL NEVER CLOSED BY OPERCULAR VALVE. 



The ovicell is w^idely open above the operculum and the opesium. 

 In the fossil forms the distal part of the mural rim is visible and not 

 modified ; the distal cicatrix left by the broken ovicell on the superior 

 zooecium is shallow. In the recent species this kind of ovicell is 

 closed by a vesicle which retracts or dilates by means of special 

 muscles to facilitate the departure of the larvae or the entrance of 

 the eggs. 



Alderina Norman, 1903, Callopora Gray, 1848, Amphihlestrtim 

 Gray, 1848, Ramphonotus Norman, 1894, and Tegella Levinsen, 1909, 

 belong to this division of the Membranipores and are well repre- 

 sented in the Early Tertiary strata of North America. 



STAMENOCELLA, new genus. 



{Stamen., in allusion to the form of the zooecium.) 



Ovicell hyperstomial, not closed by the opercular valve. No 



dietellae. Gymnocyst long and flat, supporting a small, sessile, 



salient avicularium. 



