DESCRIPTIONS OF SPECIES. 339 



POLYPORA sp. a. 



This species occurs associated with that provisionally identified as P. cestriensis 

 Ulrich. It resembles the latter in many particulars, the chief difference which the 

 scantjT and imperfect material exhibits being that the unidentified form is distinctly 

 more finel}' reticulated. As in P. cestriensis, there are four rows of zooecia, and the 

 nonporiferous side is marked with sharp, fine stri^. 



Locality and Iwrizon. — San Juan region (station 2331); Hermosa formation. 



POLTPOEA sp. h. 



Another undetermined species of Polypura is found at station 2235 in the San 

 Juan region. The frond is rather rapidly enlarging, the branches thick, the dissepi- 

 ments thin and long. The fenestrules are nearly square or subcircular. The only 

 specimen observed shows the poriferous side, where the zocecia are seen to be 

 arranged in about four rows. 



Locality and horizo)i. — San Juan region (stations 2205, 2285); middle portion 

 of the Hermosa formation. 



FENESTELLA Lonsdale, 1839. 

 Fenestella cf . TENAX Ulrich. 



1888. Fenestella tenax. Ulrich, Soi. Lab. Denisoii Univ., Bull., vol. 4, p. 71. 



Waverly group: Cuyahoga County, Ohio. 

 1890. Fenestella tencu. Ulrich, Geol. Surv. Illinois, Kept., vol. 8, p. 546, pi. 51, figs. 2-2e. 



Warsaw beds: Monroe County and Warsaw, 111. 



Chester group: Chester and Kaskaskia, 111.; Sloans Valley, Ky. 

 1895. Fenestella tenax. Keyes, Missouri Geol. Surv., vol. 5, p. 24. (Date of imprint, 1894.) 



Kaskaskia limestone: Chester, 111. 



This .species is already credited with a long range, since it is found from 

 the Waverly group into the Chester, and this will be considerably increased if 

 the present identification proves correct, as is not unlikely. This form presents 

 a very fine, regular network, in which the dissepiments are more slender than 

 the branches. The latter are marked by comparatively strong, sharp, flexuous, 

 longitudinal strife. There are about five zorecia opjiosite two fenestrules, which 

 are subrectangular ujion the nonporiferous side and elliptical upon the other. 



Locality and horizon. — San Juan region (station 2331); Hermosa formation. 



Fenestella sp. 



This foi'm, which is probably the same in the San Juan and Leadville regions 

 (stations 2221 and 2265, respectivelj'), is indeterminable from the material in hand. 

 It differs from that briefly described as P. tenax in having the fenestrules 

 nearly square or subcircular, the dissepiments thicker, and the nonporiferous 



