INVERTEBRATES. 415 



shaped cavities, with salient tuberculated lips, bottoms of the 

 cups having sometimes deep lanceolate, or oval depressions; 

 interior surfaces marked with irregular ridges covered by cell 

 pores or chalices, leaving occasional abortive spaces betwee'n 

 them. This is separated from the preceding species on account 

 of its more robust growth, the irregular notched or tubercula- 

 ted form of the lid, and the other characters assigned to it 

 above. The thin and salient lips of the plumosum would 

 scarcely assume the tuberculated form in a regular develop- 

 ment of the polyzoum. 



Geological position and locality : Lower beds of the St. Louis group; War- 

 saw, Illinois. 



COSCINIUM SAGANELLA, Prout. 



PI. 22, fig. 5. 

 Coscinium saganella, Prout, 1860. Proceed. St. Louis Acad. Sci., vol. 1, p. 572. 



Polyzoum expanding and encrusting; cell divisions very 

 long, more or less irregularly hexangular, border of the septa 

 not as acute as in G. plumosum. I have provisionally sepa- 

 rated this from the two species above, until we are able to pro- 

 cure more perfect specimens. Named from its resemblance to 

 Saganella, Hall. 



Geological position and localiti/ : Lower beds of the St. Louis group; War- 

 saw, Illinois. 



Coscinium tuberculatum, Prout. 



PL 22, fig. 6. 

 Coscinium tuberculatum, Prout, 1860. Proceed. St. Louis Acad. Sci., vol. 1, p. 573. 



Polyzoum an expansion somewhat concave and broadly 

 recurved toward one margin ; tuberculations more or less 

 irregularly arranged in lines, with rythmical dimples marking 

 their summits ; those towards the upper border are not dim- 



