450 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Affinities. — As the figured specimen is the only one found we are able to get 
only an imperfect idea of this very remarkable species. The attenuation of the 
rimule-spiramen in this species and in some other species of the same family is 
always an indication of a reinforcement of the operculum more chitinizecl and 
more rigid. 
The species differs from Leiosella orlnculnria in its larger micrometric dimen- 
sions and the absence of small frontal avicularia. 
Occurrence. — Vicksburgian (“Chimney rock” of Marianna limestone): One 
mile north of Monroeville, Alabama (very rare). 
Holotype. — Cat. No. 64296, IJ.S.N.M. 
LEIOSELLA ORBICULARIA, new species. 
Plate 91, figs. 22, 23. 
Description. — The zoarium is free, cylindrical, formed of two separable 
lamellae. The zooecia are distinct, almost orbicular; the frontal is smooth and 
convex, formed of a very thick olocyst. The peristomice is large, orbicular, placed 
in the middle of the zooecia; the rimule-spiramen is formed on one side by the 
oral avicularium ; the aperture is elongated, very oblique, somewhat oval, the point 
below. On the border of the peristomie there is a large oral avicularium triangular, 
not salient, with thin wall, provided with a pivot. There are some small frontal 
avicularia, simple and orbicular, scattered among the peristomices. 
Measurements. — -Peristomice \hpe=0. 20-0.30 mm. r/ . |Zs=0.50 mm. 
(interior) \?pe=0.25 mm. J °° CCia 17^=0.40-0.45 mm. 
Affinities. — Only two specimens have been found. The great difference in 
form and position between the peristomice and the apertura is verv remarkable. 
We are ignorant of the ovicell. 
The species differs from Leiosella grandisora in its smaller micrometric dimen- 
sions and the presence of small frontal avicularia. 
Occurrence. — Vicksburgian (Red Bluff clay) : Red Bluff, Wayne County, Mis- 
sissippi (rare). 
Holotype. — Cat. No. 64294, IJ.S.N.M. 
Genus METROCRYPTA Canu and Bassler, 1917. 
1917. Metrocrypta Cantj and Basst.er, Synopsis American Early Tertiary Clieilostome 
Bryozoa, Bulletin 96, United States National Museum, p. 49. 
The frontal is a tremocyst with tubules. The rimule-spiramen is wide and 
of very little depth. Ovicell unknown. 
Genotype. — Metrocrypta Imcculenta Canu and Bassler, 1917. Jacksonian. 
The ovicell of this genus is unknown and it is therefore very doubtful that it 
should be introduced into this family. The oral avicularium is very rare; how- 
ever, its presence seems to us the best character for classification. 
