305 



Zoecial apertures are small, separated completely by mesopores, and 

 occur in diagonal and loiifiitudinal rows ; 10 zoecia iu 2 mm. diagonally and 

 7 in 2 mm. lonj^itudinally. The vestibular walls of the zooecia and meso- 

 pores are distinctly j,M-aiiuiar aloiiK the contact, forming an encircling dark- 

 band. The orifices of the zooecia lie at the base of sloping vestibules which 

 are composed of homogenous tissue forming a ring about the opening. 



As shown in the longitudinal section the zooecial tubes are thin-walled 

 in the primitive region and lie pi'ostrate upward on the median lamina, 

 then turning outward, opening into the vestibules acutely. The walls -of 

 the vestibules terminate almost perpendicularly at the ixjriphery. A single 

 liiaphragm crosses many of the zooecial tubes usually shortly preceding the 

 turn from the reclining position towards the vestibule. 



The mesopores are short, rising In the late primitive zone. True dia- 

 phragms are absent, but in some thick irregularly arranged tabulae occur. 



This species differs from Stictoporella crihrona, in having smaller fen- 

 estrules, a granular band surrounding the apertures of the mesopores and 

 zooecia, more numerous mesopores and diaphragms crossing the zooecia. 

 The zoaria of the other species is so different from >*?. cribilina that no other 

 differentiating characters are necessary. 



Occurrence : Pierce limestone. Murfreesboro. Teimessee. and 1 mile 

 north of McFadden Ford. Rutherford County. Tennessee. 



Holotype : 5010.2 U. S. Nat. Mus. 



Paratype : 2P>^. 20. 21 ; 242-13. Indiana University. 



I'^i.?- 1- — A portion of the eastern part of the United States showing the probable 

 in.lary of the Early Stones Kivci- (.Mosheini) Sea. 



