NORTH AMERICAN EARLY TERTIARY BRYOZOA. 479 



Genus CYSTISELLA Canu and Bassler, 1917. 



1917. Cystisclla CANU and BASSLER, Synopsis American Early Tertiary Oheilostome Bryozoa, 

 Bulletin 96, United States National Museum, p. 53. 



The frontal is an olocyst. It bears a very wide avicularian chamber in which 

 there is a pair of large glands. The mandibles have a lucida in the middle. 

 (Waters). 



Genotype. Cystisella (Porella) saccata Busk, 1856. 



Range. Midwayan-Recent. 



"In Porella saccata it [the ovicell] is many layered, as thin calcareous layers, 

 presumably gymnocyst [our olocyst] layers, continually grow over the ooecium, not 

 only from the distal zooecium but also from the two neighboring zooecia, and 

 we can see as a rule three, distinctly separated, thin covering plates on their sur- 

 face." (Levinsen, 1909, p. 336.) 



CYSTISELLA MIDWAYANICA Canu and Bassler, 1917. 



Plate 8, figs. 5, 6. 



1917. Cystisclla midwayanica CANU and BASSLER, Synopsis American Early Tertiary 

 Cheilostome Bryozoa, Bulletin 9G, United States National Museum, p. 53. pi. 5, fig. 6. 



Description. The zoarium incrusts shells. The zooecia are distinct, somewhat 

 elongated, hexagonal, separated by a furrow or a thin salient thread ; the frontal is 

 very convex and very finely granulated. The peristome is thin, little salient in its 

 distal part; it bears some spines; the peristomice is elliptical and deformed infe- 

 riorly by the avicularium. The avicularium forms a long chamber, median and 

 conical ; its orifice is little circular and turned toward the apertura. 



.* Ihpe=0.l0mm. . [Zs=0.40 mm. 



Measurements. Feristomice i , Zooecia , 7 



[IpeO.limm. lfe=0.30mm. 



Occurrence.- Midwayan (Clayton limestone) : Luverne, Crenshaw County, 

 Alabama (very rare) ; one mile west of Fort Gaines, Georgia (rare). 

 Cotypes.Czt. No. 62606, U.S.N.M. 



Genus PORELLA Gray, 1848. 



1848. Porella GRAY, List of British Animals in collection British Museum. Ceutroniae, 

 pp. 127, 148. 



The ovicell opens into the peristomie; it is porous, imbedded in the distal 

 zooecium. The apertura is semilunar. Neither lyrula nor cardelles. The oper- 

 culum is almost straight in its proximal part, with rounded corners: there is a 

 muscular prominence a little distance from the edge. In front of the apertura 

 there is an avicularium; the mandible is semicircular and has well marked thick- 

 enings formed of diagonal bars. The frontal is a tremocyst with tubules. 20 tenta- 

 cles. 



Genotype. Porella (Millepora) cervicornis Pallas, 1766. 



Range. Lutetian-Recent. 



