452 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Stomachetosellidae. When it exists, the oral avicularium is indeed in its place 

 in the immediate vicinity of the peristomice and of the rimule-spiramen. 



OCHETOSELLA JACKSONICA Canu and Bassler, 1917. 



Plate 15, figs. 1-10. 



1917. Oclietosella jncksonica CANU and BASSLER, Synopsis American Early Tertiary Cheilo- 

 stome Bryozoa, Bulletin 96, United States National Museum, p. 50, pi. 5, fig. 3. 



Description. The zoarium is free, erect, cylindrical, bifurcated, often anasto- 

 mosing. The zooecia are elongated, distinct, hexagonal, separated by a salient 

 thread ; the frontal is concave, bordered by large areolae, formed of a thin olocyst 

 and covered by a uniform and finely granulated pleurocyst. The apertura is semi- 

 lunar and invisible externally; the peristomice is very oblique, with undefined 

 outlines, vaguely triangular. The ovicell is globular and deeply imbedded in the 

 distal zooecia. The oral avicularium is rare. 



. 17:2=1.10-1.20 mm. 

 Measurements. Zooecia , n ,. 



{(3=0.50 mm. 



Variations. The young zooecia have no separating thread (figs. 3-6) ; they 

 have a mucro much developed and quite prominent (figs. 4, 5) which bears the 

 characteristic small canal. The zooecia are thickened by the development of the 

 pleurocyst which is deposited at first around the areolae (fig. 9) and afterwards 

 over all the frontal (fig. 8). In these conditions, the .mucro is of less and less 

 prominence, but the small canal-like spiramen always persists. This same pleurocyst 

 covers the ovicell (figs. 3, 10). 



At the bifurcation of the branches, there is a large zooecium which bears a 

 large special avicularium whose purpose is still to be learned. 



Affinities. This species is very easy to determine. It differs from Ochctosclla 

 robusta in its smaller zoarium, in its large, lateral areolae and in the absence of 

 the zooecial peristomie. 



Occurrence. Upper Claibornian (Gosport sand) : One mile southwest of 

 Rockville, Clarke County. Alabama (very rare) ; Gopher Hill, Tombigbee River. 

 Alabama (rare). 



Lower Jacksonian (Mooclys marl) : Jackson, Mississippi (very common). 



Middle Jacksonian: Wilmington, North Carolina (very common) ; near Lenuds 

 Ferry, South Carolina (common) ; Eutaw Springs, South Carolina (common) ; 

 3^ miles south of Perry, Georgia (common) ; 18 miles west of Wrightsville, Georgia 

 (common) ; Rich Hill, Crawford County, Georgia (very common) ; Baldock, Barn- 

 well County, South Carolina (very common) ; 17 miles northeast of Hawkinsville, 

 Georgia (rare) ; one-half mile southeast of Georgia Kaolin Company mine. Twiggs 

 County, Georgia (rare). 



Upper Jacksonian (Ocala limestone) : West bank Sepulga River. Escambia 

 County, Alabama (rare). 



Cotypes.Czt No. 62599, U.S.N.M. 



