NORTH AMERICAN EARLY TERTIARY BRYOZOA. 289 



The g-ymnocyst which surrounds the cribriform area is very inconstant and is 

 developed chiefly in the lower part of the zooecia. 



This species differs from M cmbraniporella subagassizi in its zoarial dimensions, 

 its much smaller micrometric measurements, and its numerous frontal lacunae. 



Occurrence. Middle Jaeksonian: Eighteen miles west of Wrightsville, John- 

 son County, Georgia (rare) ; one-half mile west of Georgia Kaolin Company's Mine, 

 Twiggs County, Georgia (rare). 



Cotypes Cat. Nos. 64017, 64018, TJ.S.N.M. 



MEMBRANIPORELLA MONILIFERA, new species. 



Plnte 41 ? figs. ',>. 10. 



Desi-ri/>/!ini. The zoarium incrusts shells. The zooecia are distinct, separated 

 by a furrow, elongated, elliptical, wide; the frontal is convex; the costules are 

 radially arranged, united near the zoarial axis, separated by long, rather wide slits, 

 and ornamented with two tuberosities of which one is a talon. The aperture i- 

 semi-elliptical and is limited by a thin peristome which bears at least two. large, 

 hollow spines and, in front, by a calcareous thickening in the form of a T. The 

 ovicell is closed by the operculum. There is a vestibular arch and four spines, 

 of which the first pair is the larger. 



fAa=0.07mm. . I Ls=0.50 mm. 



Measurements. Aperture,, _ _ /ooecia 



U=0.0i mm. 



Variations. This species is characterized by its two costular tuberosities; 

 one is at the aperture itself and the other is close to the zooecial axis. The general 

 effect of these tuberosities is that of a double necklace around the zooecia. 



The part formed by the union of the costules forms in front of the zooecia a 

 sort of shield of variable size. 



Very often the costular tuberosities do not exist; the zooecia then have the 

 ;i-|>rct of a very simple MembraniporeUa. 



There are no lumen pores. 



Affinities. This species differs from Mcmbraniporella bioculata in its smaller 

 micrometric dimensions, the absence of oral avicularia, and the presence of tuberosi- 

 ties on the costules. In its incrusting zoarium it differs from all the other species 

 of MembraniporeUa studied. 



Occurrence. Middle Jacksonian: near Leimds Ferry, South Carolina (rare) ; 

 Eutaw Springs. South Carolina (rare). 



Cotypes. Cat. Nos. 64019, 64020, TJ.S.N.M. 



MEMBRANIPORELLA (?) SUBAGASSIZI, new species. 



Plate 84, figs. S-13. 



Description. The zoarium is free, cylindrical, formed of five or six longitudinal 

 rows of zooecia. The zooecia are large, distinct, separated by a furrow, elliptical; 

 the frontal is very convex and formed by a cribriform area surrounded by a 

 smooth gymnocyst; the cribriform area contains 10 to 12 transversal and radial 

 costules. Each costule is separated from its neighbor by a large lacuna followed 

 r,f.SM in Bull. 106 -- 19 



