Mea-wn-tu, nts.- 



NORTH AMERICAN EARLY TERTIARY BRYOZOA. 839 



Distance between the lines 0.2-10.26 mm. 



Width of the lines 0.20 mm. 



Diameter of the peristome 0.10-0.12 mm. 



Maximum width of the branches 1.25 mm. 



Variations. The polymorphism of this species is unprecedented. If the 

 number of the specimens found had not permitted the discovery of the intermediate 

 forms, it. might have appeared that many new species were represented. An inter- 

 esting variation is that shown by the young branches; the tubes do not bear any 

 vacuoles: their frontal is concave, bordered laterally, and of a microscopic structure 

 analogous to that of the other Cyclostomata. 



The longitudinal section shows very numerous vacuoles. The successive 

 lamellae have no regularity; they appear to be formed by very thick walls of 

 tergopores irregularly branched and entangled. This is therefore only one aspect 

 of lamellar structure. In transverse section these pseudo-lamellae are still more 

 irregular; they appear to result from the juxtaposition of the tergopores arranged 

 parallel to the basal lamella. 



The tangential section of the dorsal shows that the vacuoles perforate a sort 

 of olocyst with large elements. 



The abrasion of the dorsal vacuoles and of the basal lamella shows that in the 

 interior the tubes have the fusiform appearance and are arranged as in the other 

 free Cyclostomata having only one cellular face. 



The zoarium is supported by an expanded base. Only a single specimen with 

 the base has been found and we have not been able to discover the ancestrula by 

 successive sections. 



Affinities. This species differs from Polyascosoecia cancellata Reuss, 1847 

 (not Goldfuss), in its fascicles which are quite close to the median crest. 



It differs from Polyascosoeoia foraminosa Reuss. 1865, in its smaller vacuoles 

 and in its fascicles not distant from the median crest. 



This may possibly be Polyascosoecia subcancellata Manzoni, 1877, but that 

 author has neglected to figure the anterior face of the zoarium, the aspect of which is 

 unknown to us. 



Occurrence. Middle Jacksonian : Rich Hill, 5^ miles southeast of Knoxville, 

 Crawford County, Georgia (very abundant) ; Baldock, Barnwell County, South 

 Carolina (common) ; 17 miles northeast of Hawkinsville, Georgia (common) ; 3^ 

 miles south of Perry, Georgia (very abundant) ; 3^ miles north of Grovania, 

 Georgia (common) ; one-half mile southeast of Georgia Kaolin Co. mine, Twiggs 

 County, Georgia (very common). 12 miles southeast of Marshallville, Georgia 

 (abundant) : Eutaw Springs, South Carolina (rare) ; 18 miles north of Wrights- 

 ville. Johnson County, Georgia (common) ; H miles southeast of Lilly, Dooly 

 County, Georgia (common). 



This species exists in almost all the localities of the middle Jacksonian, although 

 it has not yet been found at this horizon at Wilmington. North Carolina. 



CotypesCsA. Nos. 65333, 65334, U.S.N.M. 



