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. 



nr rr \Ls=0.20 mm. , 7 ., n \Lv=0.15 mm. 



Measurements. Zooecia , Vibracula 7 ^ 



|te=0.15 mm. \lv=Q.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 (?s=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 Lumdaria 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 1'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. OtioneUa CANU ami 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. OtioneUa perforate. 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 



