NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
105 
the mural rim is thin, sharp, irregular, and gashed. The opesium is irregular. 
The ancestrular zooecia never cover the grain of quartz to which the larva affixes 
itself. The vibracula are not very constant; they are at first very small, increas- 
ing in size toward the periphery and becoming primoserial. On the inner face 
the radial rows are flat, smooth at the center, very porous at the circumference. 
Measurements. — Zooecia 
jZs= 0.20 mm. 
\lz— 0.15 mm. 
Vibracula] 
l 
Zn=0. 15 mm. 
Zr=0.07 mm. 
Affinities. — This is a very typical Trochopora and is the species corresponding 
to Trochopora subplena Reuss 1855, of the European Oligocene. It differs from it, 
however, in its smaller opesial dimensions (ls= 0.15 mm. instead of 0.20-0.24 mm.). 
When altered by fossilization Trochopora truncata is difficult to distinguish 
from badly preserved examples of lumilaria ligulata , with which it very often 
occurs. The specimens with a flat and perforated base may alone be considered as 
Trochopora truncata. 
Vertical sections are not always necessary to discover the heaped-up disks, for 
they are often visible in partial fractures. 
De Gregorio’s figures are rather mediocre, but as his text apparently agrees . 
with our specimens, we believe it necessary to adopt his name : “ Testa superne 
truncata plus minusce discoidea. ... Le type de cette variete s’eloigne 
beaucoup du type de l’espece, de sorte qu’on pourrait le considerer comme une 
espece differente . . . figs. 34-37 couche detachee de la face inferieure (disk).” 
Occurrence. — Claibornian (Gosport sand) : Gopher Hill, Tombigbee River, 
Alabama; 1 mile southeast of Rockville, Alabama (rare); Claiborne, Alabama 
(very abundant). 
Claibornian (Cook Mountain formation) : Moseleys Ferry, Caldwell County, 
Texas (abundant). 
Lower Jacksonian: 3| miles southeast of Shell Bluff post office, Georgia (rare). 
Lower Jacksonian (Moodys marl) : Jackson, Mississippi (abundant). 
Plesiotypes. — Cat. No. 63838, U.S.N.M. 
Genus OTIONELLA Canu and Bassler, 1917. 
1917. Otionella Canu and Bassler, Synopsis of American Early Tertiary Bryozoa, Bulletin 
96, United States National Museum, p. 13. 
The zoarium is discoidal (Lunulites form), with neither ovicell nor radicular 
and hydrostatic zooecia. The vibraculum is interzooecial, unsymmetrical, auricu* 
lated, one lip more prominent than the other. The zooecia are hexagonal and dis- 
posed in quincunx on the outer face and in radial lines on the inner side. The 
ancestrula is as large as the other zooecia and of the same form. 
Genotype. — Otionella perforata i Canu and Bassler, 1917. 
Range. — Campanian, Jacksonian. 
Lunulites mitra Hagenow, 1839, belongs to this genus. 
This genus is a Membranipore with the Lunulites form; that is to say, the 
colony is discoidal. It is a recognized fact that these Lunulites forms of growth are 
