BRYOZOA. 509 



they and the dissepiments being wider and the branches nar- 

 rower than on the obverse side. 



A variety of this species is represented by figs. 3 and 3a. It 

 is from the Coal Measures in Montgomery Co., 111., and differs 

 from the typical form in having three as the prevailing number 

 of zooecia ranges, narrower branches, and wider, subquadrangu- 

 lar fenestrules. The zocecia are also a little larger, there being 

 only eighteen or nineteen in 5 mm. The form represented by 

 figs. 4 and 4a, is also from the Coal Measures. It agrees more 

 closely with the typical form, differing mainly in having the 

 fenestrules slightly shorter and the dissepiments correspondingly 

 stronger. In the number of cell rows it is intermediate between 

 the Chester form and the Montgomery Co. variety. 



Position and locality: Chester group, Chester, 111., and Mon- 

 roe Co., 111. Coal Measures, Montgomery Co., 111., and near Red 

 Oak, Iowa. 



POLYPORA APPROXIMATA Ulrich. 



PI. LXI, Figs. 5-5a. 



Polypora biarmica Prout, (non Keyserling) 1859. Trans. St. Louis Acad. Sci., vol. 1, 

 p. 450. 



This is probably only a well marked variety of P. spinulifera,, 

 but it is sufficiently distinct to deserve a name. It differs in 

 the following respects: The zoarium is stronger and in every 

 way presents a more robust aspect, the branches and dissepi- 

 ments being somewhat wider, and the fenestrules larger, espe- 

 cially upon the reverse side. There are seven to nine fenestrules 

 instead of ten or eleven. The number of cell ranges increases 

 quite regularly from three or four just after a bifurcation, to 

 six or seven before the next division. The nodes or spines are 

 stronger, much less in number, and generally occupy only 

 the center of the branches.* 



Position and locality: Chester group, Chester, 111.; Sloan's 

 Valley and Litchfield, Ky. 



*I have lately collected several hundred examples of this species, showing it to be a 

 constant form and qui e distinct from P. spinulifera. The specimens were obtained 

 from near Clayton P. O., Caldwell Co., Ky., where they occurred in a bed of shaly 

 limestone at the top of the Chester. 



