618 PALAEONTOLOGY OF ILLINOIS. 



Primary portion of zooecia as well as their apertures in two 

 alternating ranges, eleven or twelve in 5 mm., the ranges sep- 

 arated by a well developed and faintly nodulose keel. Aper- 

 tures circular, widely sparated longitudinally, about 0.1 mm. in 

 diameter. Hemisepta well developed. 



The specimen from which the above description is drawn 

 shows only the reverse, and was at first supposed to belong to 

 P. flexuosa. The more strongly striated reverse, and more 

 numerous pinnae, led me to make another examination. Thin 

 sections were prepared and these proved conclusively that it 

 belonged to a very different species, having a marked carina 

 and the primitive portion of the zooecia in both the branchlets 

 and midrib in two ranges. P. flexuosa, as may be seen on PI. 

 LXVI, fig. 4a, has the zooecia of the branchlets practically in 

 one range. P. vinei has shorter zooecia and a greater number 

 of branches, while in P. youngl the latter are shorter and more 

 numerous. 



Position and locality: Keokuk group; Bentonsport, Iowa. 



PlNNATOPORA CONFERTA Ulrich. 

 PI. LVI, fie. 5. and PI. LXVI. fig. 6. 



Zoarium pinnate; midrib about 0.7 mm. wide, finely striate 

 on the reverse, with the carina on the obverse face elevated, 

 rounded, and, when perfect, bearing prominent nodes 1 mm. or 

 less apart. Lateral branches also carinate, with somewhat 

 closer nodes, 1.5 mm. long, about two-thirds as wide as the 

 midrib, of the same width throughout, separated by interspaces 

 very little wider than themselves, almost opposite on the two 

 sides, ten in 1 cm., given off at an angle of about 60. Aper- 

 tures rather large, circular or slightly oval, 0.15 mm. in dia- 

 meter, with very faint peristome, about their own diameter 

 apart, with fifteen in 5 mm. 



The distinctive features of this species are the large zooecia 

 apertures and the strong and closely arranged lateral branch- 

 lets. 



Position and locality: Keokuk group, Keokuk, Iowa and 

 Jersey Co., 111. (Otter Creek). 



