834 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Variations. The great number of peristomes and mesopores which ornament 

 the surface of this bryozoan give it a very characteristic porous aspect. Moreover, 

 the oval peristomes are unique in the genus. The longitudinal sections which we 

 have made are not very clear. They simply indicate the superposition of the multiple 

 layers composing the zoarium. The walls of the tubes and mesopores do not appear 

 vesicular. 



In its exterior aspect this species much resembles Lichenopora, especially if 

 we observe the oval form of the peristomes. But the nature of its ovicell does not 

 permit that it be classed with these well-known bryozoa. 



Occurrence. Middle Jacksonian: Eutaw Springs, South Carolina (common). 



Cotypes. Cat. No. 65368, U.S.N.M. 



PARTRETOCYCLOECIA EXILIS, new species 



Plate 160, tigs. 5-16. 



Description. -The zoarium is hollow, cylindrical, bifurcated, with large central 

 cavities and thin walls. The tubes are club-shaped in their lower part and cylin- 

 drical where the mesopores are developed (in section). The peristomes are thin, 

 orbicular, hardly salient, arranged vaguely in very irregular, transverse rows. The 

 ovicell is orbicular, somewhat salient, pierced by tubes each of which is accompanied 

 by a mesopore. 



Diameter of the peristome 0.10-0.12 mm. 



Diameter of the mesopores 0.08 mm. 



Diameter of the ovicell 1.65 mm. 



Diameter of the branches 3.00 mm. 



Variations. The peristomes are salient (figs. 9, 10) or not (figs. 11, 12). The 

 mesopores are small (fig. 9), medium (fig. 10), or large and polygonal (fig. 12), 

 according to the degree of weathering. 



In the longitudinal section it is impossible to confirm the nature of the tubes, 

 whether they are cylindrical or club-shaped. 



Affinities. In its exterior aspect this species much resembles Partretocydoecia 

 dumosa Ulrich, 1901. It is distinguished from it only by its micrometric dimen- 

 sions, in its smaller ovicell, and in its larger internal cavities. The size of the 

 latter is in fact very characteristic. 



Occurrence. Vicksburgian (Marianna limestone) : One mile north of Monroe- 

 ville, Alabama (very common). 



Cotypes. Cat. No. 65413, U.S.N.M. 



Family ASCOSOECIIDAE Canu, 1919. 



1019. Ascosoeciidae CANTJ, Etudes sur les Ovicelles des Bryozoaires Cyclostomes (2), 



Bulletin Soci6t6 Gologique de France, ser. 4, vol. 17, p. 346. 



The ovicell is a large, elliptical, elongate swelling quite salient and perforated 

 by the tubes ; often a median oeciopore is present. 



Measurements.- 



