544 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



them are not provided with an ascopore. We have as yet collected no segment 

 preserving the base, and we arc therefore ignorant of the signification of these pores. 

 It may be presumed that one pore is intended for the chitinous joint and the other 

 for a radicell (figs. 6. 7). 



The tubules in becoming elongated also increase the diameter of the segments 

 and the width of the zooecia (figs. 8, 9) : but this is a very rare variation. The 

 peristomiale presents pores a little larger and arranged at the base of longitudinal 

 canals. 



The ovicells are large convexities, of which the external apertures (0.20 mm.) 

 are much larger than those of the ordinary zooecia (0.12 mm.). 



At the locality near Perry. Georgia, a segment was found with large pores 

 and with very thick peristomes. which we think belongs to this species (fig. 10), 

 but of this we are not absolutely certain. 



Affinities. This species differs from Tubucellaria parviporosa in having some- 

 what larger pores and much shorter zooecia (Zs=1.10 mm. instead of 1.30 mm.). 

 It may be distinguished from Tulmcellaria vicksburgica by its smaller frontal 

 pores, its shorter zooecia (1.10 mm. instead of 1.40 mm.), and by its system of 

 articulation, which does not have a very salient process. 



This species is rather deceiving in its qnite variable external aspect. It may 

 only be determined with certainty by the aid of micrometric measurements; it is 

 the smallest of the American Tvbucellaria. 



Occurrence. Middle Jacksonian: 18 miles west of Wrightsville, Johnson 

 County, Georgia (rare) ; 3J miles south of Perry, Georgia (rare) ; one-half mile 

 southeast of Georgia Kaolin Co. mine, Twiggs County, Georgia (rare) ; 17 miles 

 northeast of Hawkinsville, Georgia (very rare). 



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

 County, Alabama (rare). 



Ootypes.Ca.t. Nos. 64183-64185, U.S.N.M. 



TUBUCELLARIA VICKSBURG1CA, new species. 



Plate 97, figs. 1-16. 



Description. The zoarium is articulated, composed of large, long, cylindrical 

 segments ; the younger segments' have only one basal pore, but the older ones have 

 two of them. The zooecia are much elongated, distinct, swollen; the frontal is 

 covered with large, polygonal pores ; the peristomiale is not distinct from the frontal. 

 The peristome is very salient, oblique, thin in the young zooecia. very thick in the 

 old ones. The ascopore is large (0.02 mm.). The ovicelled zooecia have a larger 

 external aperture. 



Old zooecia. Yonns zoofcia. 



I Peristomice=0.16 mm. =0.12 mm. 



Measurements.'^ . 



lPenstome=0.30 mm. 0.18 mm. 



. fL,3=1.40mm. =1.40 mm. 



I/.? =0.60-0.65 mm. =0.50-0.60 mm. 



