BRYOZOA. 515 



ridges are thinner, being abruptly elevated from the nearly flat 

 bottom of the cups. The cups are also much shorter, many of 

 them being hexagonal in outline and but little longer than 

 wide. In an average example their dimensions may vary as 

 follows: the width from 3 to 7 mm.; the length from 5 to 10 

 mm.; the depth from 1.5 to 2.5 mm. The dimples are also 

 much better defined and more depressed, one placed near the 

 center of the cup being especially distinct and generally of elon- 

 gate stellar form. A number, varying with the size of the cup, 

 are arranged in a subradial manner around the central one, 

 and extend up the steep slopes of the ridges to the sharp non- 

 poriferous edge. The zooecial apertures are also shown more 

 closely approximated. 



Position and locality: Warsaw beds. Common at Warsaw, 

 111. A small example of this variety is figured in Vol. 2 of this 

 Survey, as the opposite side of Coscinium plumosum Prout, 

 obviously in error. 



GLYPTOPORA SAGENELLA var. LATA Ulrich. 



PL LXXVni, fig. 4. 



This variety differs from typical G. sagenelhi in very nearly 

 the same manner as does the var. m Jiculosa, its principal pecu- 

 liarities being the much wider cup and the more elongated and 

 often curved dimples. The figure represents one side of an aver- 

 age example. 



Position and locality: Warsaw beds. Xot rare at Warsaw, El. 



GLYPTOPORA MICHELFXIA Prout. 



PI. LXXVm, fig. 8-86. 



Coscinium michelinia Prout, 1800. Trans. St. Louis Acad. Sci. Vol. I, p. 573. 

 Coscinium micheUniaProut, 1866. Geol. Surv. El. Vol. 2, p. 414, PI. XXH, fig. 4, 4o. 



Zoarium encrusting or free, with a wrinkled epitheca on the 

 lower side. Upper surface divided into larger or smaller, deep, 

 polygonal, cup-shaped cavities, enclosed by prominently elevated, 

 sharp ridges, the summits of which, when in a good state of 



