150 NORTH AMERICAN INDEX FOSSILS. 



1 06. P. submarginata Meek. (Fig. 205, c) Carbonic. 

 Branches convex with a row of spines or tubercles, and five 



ranges of apertures; five or six apertures to a fenestrule, the latter 

 irregular, elongate oval ; dissepiments thin. 



Upper Coal Measures of Nebraska, Iowa and Illinois. 



LIX. Thamniscus King. 

 Branches like those of Polypora, but bifurcating more freely and 

 rarely or not at all connected by dissepiments. Sil.-Carb. 



107. T. furcillatus Ulrich. (Fig. 205, e.) Mississippian. 

 Branches small, with three to four ranges of apertures, with con- 

 tinuous or discontinuous low ridges between. 



A characteristic species of the Chester group of Illinois and 



Kentucky. 



LX. Lyropora Hall. 



Flabellate, the fenestrated portion spread between the arms of 

 a non-poriferons U- or V-shaped calcareous support, which is free 

 or pedunculate at the base ; zocecia in from two to five ranges ; no 

 median keel. Miss. 



108. L. quincuncialis (Hall). (Fig. 205, d.) Mississippian. 

 U-shaped support narrow oval in cross section ; fenestrules ir- 

 regularly oval ; two or three ranges of apertures ; stout dissepi- 

 ments, which, on the non-celluliferous side, are often stronger than 

 the branches, forming transverse ridges. 



Chester of Illinois and Kentucky. 



LXI. Fenestralia Prout. 

 Differs from Fenestella in having four rows of apertures, two on 

 each side of prominent keel. Miss. 



109. F. sancti-ludovici Prout. Mississippian. 

 Branches with strong central carinas dilated into tubercles at 



intervals ; fenestrules oblong, subquadrangular ; two ranges of 

 apertures on each side of carina ; dissepiments about two-thirds the 

 width of the branches. 



Warsaw and St. Louis of Missouri and Illinois. 



LXII. Pinnatopora Vine. 

 Small, delicate stipe, and short, free lateral branches given off at 

 regular, intervals ; apertures in two rows on one face only, separ- 

 ated by a moderate median keel. (Glauconome of authors.) 

 Dev. - Carb. 



