830 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Variations. — The zoaria are not always reticulate; it is frequent to find 
branches free, smooth, or spinous. The relative arrangement of the apertura and 
mesopores is that of Sparsicavea ; the zones are almost always transversal, but 
very irregular (fig. 3). The mesopores are sometimes closed by a calcareous 
lamella. 
An excellent longitudinal section permitted us to study the branching of 
the zoaria (fig. 11). At the center of the zoarium and quite distant from the 
bifurcation, two tubes diverge, an axial tube to the left and an axial tube to the 
right; their successive ramifications diverge necessarily in forming the two zoarial 
branches. 
The mesopores have a diameter almost equal to that of the tubes; this char- 
acter is not visible in the tangential sections (fig. 13). The zones of mesopores 
appear to be formed of branched mesopores (figs. 11, 12). 
A-ffi.nities. — In its reticulate zoarium and in the aspect of its surface, this 
species is identical with Ascosoecia ulrichi ; it differs from it in its somewhat larger 
apertura (0.12 and not 0.10 mm.). 
Occurrence. — Middle Jacksonian: Near Lenuds Ferry, South Carolina (rare) ; 
Eutaw Springs, South Carolina (very common). 
Cotypes.— Cat. No. 65374, U.S.N.M. 
Genus PARTRETOCYCLOECIA Canu, 1919. 
1919. Partetrocycloecia (in error for Partretocycloecia) Canu, Etudes sur les Ovicelles 
des Bryozoaries Cyelostomes (2), Bulletin Soeiete Geologique de France, ser. 4, 
vol. 17, p. 346. 
The tubes are club-shaped. 
Genotype. — Partretocycloecia ( Cavaria , ) dumosa Ulrich. 
Range. — Midway an-Vicksburgian. 
All the known species of this genus have hollow zoaria ( Cavaria form of 
growth). The tubes are short and their club-shaped form does not appear very 
clearly in transversal sections. It would be preferable to chose a genotype with 
a solid zoarium. 
Another consequence of the contraction is to transform certain mesopores into 
aborted tubes ; that is to say, into dactylethrae. 
PARTRETOCYCLOECIA DUMOSA Ulrich, 1901. 
Plate 103, figs. 1-14. 
1901. Cavaria dumosa Ulrich, Maryland Geological Survey, Eocene, p. 208, pi. 59, figs. 4-8. 
Description. — The zoarium is free, hollow, branched, dichotomous, arborescent. 
The tubes are short, club-shaped, cylindrical, with their extremity bent (in section). 
The peristomes are orbicular, hardly salient, thin, irregularly distributed in quin- 
cunx. The mesopores are smaller, polygonal, but rounded and (in section) with 
thick walls. The ovicell is large, smooth, perforated by the tubes; each tube is 
accompanied by a single mesopore. 
