826 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Family TRETOCYCLOECIIDAE Canu, 1919. 



1919. Tetrocyclucciidae (in error for Trctocyclocciidae) CANU, Etudes sur les Ovicelles des 

 Bryozoaires Cyclostonies (2), Bulletin Societe Geologique de France, ser. 4, 

 vol. 17, p. 346. 



The ovicell is orbicular, flat, not salient, smooth, regular, and limited, traversed 

 by tubes and sometimes by mesopores adjacent to the latter. 



This family has a resemblance to the Diaperoeciidae, but differs from it in the 

 flat orbicular and not globular form of the ovicell, and in the presence of the 



mesopores. 



Genus TRETOCYCLOECIA Canu, 1919. 



1919. Tetrocycloecia (in error for Tretocycloecia) CANU, Etudes sur les Ovicelles des 

 Bryozoaires Cyclostomes (2), Bulletin Societe Geologique de France, ser. 4, 

 vol. 17, p. 346. 



The tubes are cylindrical. The mesopores are irregularly directed; their walls 

 are vesicular. The tubes which perforate the ovicell are accompanied by the 

 adjacent mesopores. 



Genotype. Tretocycloecia (Heteropora) dwhotoma Reuss, 1817 (not Hage- 

 now, 1851). 



Range. Midwayan-Tortonian. 



TRETOCYCLOECIA (?) ATTENUATA Ulrich, 1882. 

 Plate 109, figs. 1-9. 



1882. Heteropora attenuata ULKICH, American Paleozoic Bryozoa, Journal Cincinnati So- 

 ciety Natural History, vol. 5, p. 144, pi. 6, fig. 12. 



1909. Sparsicavea attenuata GBEGOBT, Catalogue Fossil Bryozoa in Department Geology 

 British Museum, Cretaceous, vol. 2, p. 302. 



Description. The zoarium is solid, cylindrical, branched, with branches 

 rounded at the summit. The tubes are cylindrical, curved at their extremity (in 

 section). The peristome is smooth, orbicular, not salient, imperfectly visible. The 

 mesopores are rare, rounded, smaller than the tubes, with very thick walls and 

 in section very short and with vesicular walls. 



Diameter of the aperture 0.08-0.10 mm. 



Diameter of the peristomes 0.10-0.16 mm. 



Diameter of the branches 2.00 mm. 



Diameter of the mesopores 0.06-0.08 mm. 



Diameter of the ovicell 1.00 mm. 



Variations. The number of the mesopores surrounding an aperture is rather 

 variable. More often there is only one mesopore between the peristomes; some- 

 times the mesopores are in groups of six or seven. The branches are sometimes 

 dichotomous and sometimes arborescent. The distance between two mesopores is 

 almost always greater than their diameter. 



The only ovicell discovered was broken; we are therefore not exactly certain 

 of our generic determination. 



Measuremen ts. 



