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. 
7 i r , . r Aa=0.14 mm 
Measurements . — Aperture \ , ,, „ 
1 [Za=0.12mm. 
Zooecia 
lz= 0.56-0.65 mm. 
Lz— 0.75 mm. 
Affinities . — The characteristic of this species is its smooth and nonporous 
frontal ; this is an exception in the genus. 
It differs from Metroperiella grandipora , in which the zoarium is also multi- 
lamellar in its larger micrometric dimensions and its nonporous frontal. 
It differs from M etropeidella 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. — Cat. No. 61068, 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 large 
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. 
M easurements . — Aperture 
k=0.1f mm. 
la— 0.17 mm. 
Zooecia 
Lz= 0.72 mm. 
k= 0.30 mm. 
Affinities . — This species much resembles the variations in Metroperiella porosa. 
It differs from M. porosa in its larger and transverse apertura (?a=0.l7 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). 
Iiolotype. — Cat. No. 64067, IJ.S.N.M. 
