NORTH AMERICAN EARLY TERTIARY BRYOZOA. 505 



Variations. The dorsal is sometimes smooth (fig. 16) and sometimes granular 

 (figs. 15. 17) ; in the latter case the lozenge-shaped areas contain a round avicu- 

 larium and an elliptical aviculnrium. In the young zooecia (fig. 14) when the 

 small labial avicularium is not yet formed the rimule-spiramen is lateral and a 

 median mucro separates it from another symmetrical slit. The aspect of the 

 frontal changes completely when the labial avicularium is much developed (fig. 

 20) ; it is elongated, triangular with a somewhat rounded beak and it occupies 

 then a part of the frontal. 



Affinities. This species differs from Retepora ramosa in which the zoarium 

 is not reticulate, in the presence of a labial avicularium. 



The rimule spiramen is the exact equivalent of the spiramen itself. A generic 

 division may not be seriously established on their differentiation. They are more- 

 over often observed together on the same zoarium. 



Occurrence. Vicksburgian (Marianna limestone) : West bank Conecuh River, 

 Escambia County, Alabama (common) ; Salt Mountain, 5 miles south of Jackson, 

 Alabama (rare) ; 2-J miles north of Millry, Washington County. Alabama (rare) ; 

 1 mile north of Monroe.ville, Alabama (common). 



Vicksburgian (Byram marl) : One-fourth mile west of Woodward. Wayne 

 County Mississippi (common). 



Cotypes.C&t. Nos. 64311-64313, U.S.N.M. 



Genus HIPPELLOZOON Canu and Bassler, 1917. 



1917. Hippellozoon CANU and BASSLER, Synopsis of American Early Tertiary Cheilostome 

 Bryozoa, Bulletin 96, United States National Museum, p. 55. 



The ovicell is widely open. There is neither labial avicularium nor reteporidan 

 pore. The operculum is contracted in the middle, having long bands at the sides 

 for the muscular attachments; the proximal edge is not straight. The aperture 

 has two cardelles. 



Genotype. Hippellozoon (Retepora) novaezelandiae Waters, 1894. Recent. 



Levinsen having introduced the genus Rhynchozoon Hincks. 1891. in the 

 Reteporidae, we have decided to adopt the suffix " zoon " as characteristic of the 

 family. It is evident that if the study of the larvae does not confirm the observa- 

 tion of Levinsen the names which we have given should not be preserved. There 

 should be no law of priority in these attempts at synthetic nomenclature. 

 Genus SCHIZELLOZOON Canu and Bassler, 1917. 



IfHT. Scliizcllozoon CANU and BASSLEB, Synopsis American Early Tertiary Cheilostome 

 Bryozoa, Bulletin 96, United States National Museum, p. 55. 



The ovicell is widely open and provided with a semicircular slit. It has neither 

 labial avicularium, nor reteporidan pore. The operculum has a broad thickened 

 border; the proximal edge is not straight. The poster of the apertura bears a wide, 

 little deep sinus. 



Genotype. Schizellozoon (Retepora) imperati Busk, 1S84. Recent, 

 The spiramen (reteporidan pore of Waters) is replaced by a pseudo-spiramen, 

 tvhich is a groove in the proximal lip of the peristomice. 



