NORTH AMERICAN EARLY TERTIARY BRYOZOA. 249 



Affinities. The vibracula arc arranged two to ever}' two zooecia (Olir/otresium 

 of Gabb and Horn) in which feature the species agrees with Lunularia contigua 

 Lonsdale, 1845, and L. vicksburgensis Conrad, 1847. 



It differs from Lunularia contigua in its solid zoarium without hydrostatic 

 zoarial cavity (fig. 13). 



It may be distinguished from Lunularia vicksburgensis Conrad, 1847, by its 

 vibracular condyles which are without depressions, by its opesial, proximal border 

 which is often convex, by the pores of the rows on the inner face which are much 

 more numerous and closer together, and by its smaller zboecial dimensions. 



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

 Clarke County. Alabama (common) ; Gopher Hill. Tombigbee River, Alabama 

 (common) ; Claiborne, Alabama (rare). 



Cotypcs.Cnt. No. 63847, U.S.N.M. 



LUNULARIA (OLIGOTRES1UM) VICKSBURGENSIS Conrad, 1847. 



Plate S3, figs. 1-11. 



1.S47. I.iinuUtcx rii-kxliiiriirnsis CONRAD. Observations on the Eocene formation, and descrip- 

 tions of one hundred and five new fossils of that period, from the vicinity of Vicks- 

 burg, Mississippi, with an appendix, Proceedings Academy Natural Sciences Phila- 

 delphia. vol. 3, p. 296: idem 1S48, Journal Academy Natural Sciences Philadelphia, 

 ser. 2, vol. 1, p. 127. 



1862. Oligotresium vicksburgensis GABB and HORN, Monograph of the fossil polyzoa of 

 the Secondary and Tertiary formations of North America. Journal Academy Natural 

 Sciences Philadelphia, ser. 2, vol. 5, p. 139, pi. 19, fig. 22. 



Description. The zoarium is a convex expanded Lunulites, without hvdrostatic 

 zooecia. The zooecia .are distinct, ogival, somewhat transverse; the mural rim is 

 very thick; the cryptocyst is very small and finely granulated. The opesium is oval, 

 narrowest at the top, the proximal border quite concave; it is bordered by a small 

 collar. The ovicell is a distal convexity hidden by the external calcification. The 

 vibraculum is very long; its opesium is large and narrowed in the upper third 

 by two large condyles with a small fossette. The vibracula are arranged in radial 

 rows, but there is only one to every two interzooecial angles. On the inner side the 

 radial lines are convex and garnished with large scattered pores. One pair of 

 lateral septulae. 



[7w=0.20mm. ,, . [,3=0.35 mm 



Measurements. Opesium , nnn ,,_ Marginal zooec-iunai, 



lw=0.20-0.2o mm. ? .?* ;^ tl n ;U2=0.3 



fZ-y=0.35mjn. 

 \ ibraculum , n nn 



U'tf=0.20mm. 



I ~ii nation*. The micrometric dimensions of the zooecia and opesia are quite 

 variable and are notably larger on the zoarial margins. The ectocyst which floats 

 in the hypostege secretes a thin calcareous granular layer, which is deposited chiefly 

 on the primitive olocyst of the cryptocyst and ovicell (fig. 2). 



The vibraculum is not always elliptical; it has sometimes a distal callosity 

 in the form of the leaf of Sagittaria (fig. 3). 



