NORTH AMERICAN EARLY TERTIARY BRYOZOA. 365 



METROPERIELLA ACERVATA, new species. 



Plate 48, figs. 1-5. 



Description. The zoarium is formed of many lamellae piled up on one 

 another, all on the same side; it probably creeps over algae. The zooecia are 

 distinct, elongated, hexagonal, bordered by a regular, salient thread. The frontal 

 is little convex, nearly flat, smooth. The aperture is small suborbicular provided 

 with a vestibular arch, formed of a semilunar anter and of a wide, rounded rimule, 

 separated by two internal condyles. The ovicell is globular, salient, completely 

 surrounding the aperture to form around it a peristomie. The median avicularium 

 is long, thin, much removed from the aperture. 



iha=0.1imm. . \lz =0.56-0.65 mm. 



Measurements. Aperture , .,_ /ooecia{ T nf ... 



[to=0.12mm. [LsO.tomm. 



Affinities. The characteristic of this species is its smooth and nonporous 

 frontal ; this is an exception in the genus. 



It differs from M etroperiella grandipora, in which the zoarium is also multi- 

 lamellar in its larger micrometric dimensions and its nonporous frontal. 



It differs from M etroperiella porosa, in which the median avicularium is long 

 and distant from the aperture, in its multilamellar zoarium, its smooth zooecia 

 and its larger zooecial length (0.75 mm. instead of 0.65-0.70 mm). 



Occurrence. Middle Jacksonian: Wilmington, North Carolina (common); 

 near Lenuds Ferry, South Carolina (rare) ; Eutaw Springs, South Carolina 

 (rare). 



Cotypes.Cnt. No. 64068, U.S.N.M. 



METROPERIELLA LATIPORA, new species. 

 Plate 47, fig. 20. 



Description. The zoarium is free and formed of two lamellae, back to back 

 and separable. The zooecia are distinct, polygonal, surrounded by a prominent 

 thread; the frontal is flat, formed of a tremocyst with small pores. The apertura 

 is large, transverse, elliptical, provided with a very wide rimule; it is larger and 

 provided with an elevated peristome in the ovicelled zooecia. The ovicell is lar^e, 

 salient, globular, somewhat embedded in the distal zooecia, smooth, completely 

 surrounding the apertura. The median avicularium is distant from the apertura. 

 long. thin, triangular, very little salient, garnished with a pivot. 



f/i,a=0.14mm. - ". "(.3=0.72 mm. 



Z 0eCia |/.r=0.30mm. 



Affinities. This species much resembles the variations in Metroperiella po>.<,i. 

 It differs from M. porosa in its larger and transverse apertura (7a=0.17 and 

 not 0.14 mm.) and in its much wider and not triangular rimule. 



Occurrence. Middle Jacksonian : Rich Hill, Crawford County, Georgia (very 

 rare) ; Eutaw Springs, South Carolina (very rare). 



Holotypc.C-at, No. 64067, U.S.N.M. 



