416 PAL/EONTOLOGY OF ILLINOIS. 



pled, and are still covered with chalices. Dimples oblong-oval; 

 in a space of twenty m m there are three to four in perpen- 

 dicular, and four in oblique lines. The mammillation is more 

 crowded towards the upper border, than near the central and 

 lower part of the expansion. I was at first disposed to 

 regard this as an irregular form of the C. Keyserlingi, but the 

 arrangement of the dimples on the summits of the mammillae, 

 and the existence of mammillary swellings instead of an irregu- 

 larly waved surface, will, it is believed, sufficiently distinguish 

 them from one another. 



Geological position and locality : Keokuk group; Warsaw, Illinois. 

 COSCINIUM ASTERIA, Prout. 



Coscinium astcria, Prout, I860. Proceed. St. Louis Acad, of Science, vol. i, p. 574. 



Polyzoum a thin, irregular encrusting expansion, covered 

 with small chalices, except at certain points, which have the 

 appearance of oblong, radiating or substellar markings formed 

 of more prominent lines of chalices, with narrow abortive spaces 

 between them. These substellar dimples are more or less 

 irregular in form, the rays being sometimes unduly prolonged, 

 but are somewhat regularly arranged in relation to one another, 

 being more or less quincuncial in their distribution. The dis- 

 tance between the substellar points is in general about 5 m. m. 



Geological position and locality: Keokuk group, Warsaw, Illinois. 



Coscinium escharense, Prout. 



PI. 22, fig. 8, 8 a. 

 Coscinium escharense, Prout, I860. Proceed. St. Louis Acad. Science, vol. i, p. 574. 



Polyzoum a flat expansion, most probably encrusting, covered 

 with small chalices except at rythmical points, where the very 



