518 . PALAEONTOLOGY OF ILLINOIS. 



well as the non-poriferous margins, are marked with fine granu- 

 lose, longitudinal striae. Apertures irregularly sub-circular or 

 oval, oblique, with strongly projecting irregularly toothed hood, 

 the average about 0.2 mm. in diameter, those bordering the 

 dimples somewhat larger; from ten to twelve occur in 5 mm., 

 measuring along the moderately regular diagonal and longitu- 

 dinal series. Interspaces somewhat rough, depressed, usually 

 of less width than the apertures. In thin sections the zooecial 

 tubes are thin-walled, at first prostrate; after bending they 

 continue in a somewhat oblique course to the surface. Vesiculae 

 small, very numerous, filled up with solid tissue towards the 

 surface. 



Position and locality: Keokuk group. Rather common at 

 Warsaw and Nauvoo, 111.; Keokuk and Bentonsport, Iowa, and 

 at other localities. 



V 



I 



GLYPTOPORA ELEGANS Prout. 



> PL LXXVIII, Fig. 10-10e. 



Coscinium elegans Prout, 1860. Trans. St. Louis Acad. Sci. Vol. 1, p. 572. 

 Coscinium elegans Prout, 1866. Geol. Sur. 111., Vol. 2, p. 413. PL XXII, Fig. 2-2a. 



In this species the growth and general construction of the 

 zoarium is precisely as in G. keyserlingi, from the Keokuk 

 group. The only differences so far observed are, (1) that the 

 cups are more numerous, proportionally smaller, and the bi- 

 foliate partitions narrower; (2) the dimples prevailingly nar- 

 rower, and (3) the zooecia apertures are smaller, their diameter 

 varying from 0.15 to 0.2 mm., with from 12 to 14 in 5 mm. 

 The smaller size of the apertures is the most important as well 

 as the most constant of the differences. 



Position and locality: Warsaw beds at Warsaw, 111. 



GLYPTOPORA MEGASTOMA III rich. 



PL LXXVIII, Fig. 5-5a. 



In its manner of growth and general appearance this species 

 resembles G. keyserlingi Prout, but the following points of dif- 

 ference are so obvious that there is little danger of confusion 

 between them. The dimples or maculae are shorter and not de- 



