INVERTEBRATES. 413 



thickened on the lower border, but not distinctly nasiform ; 

 direction of the cells, slightly upward and outward to the plane 

 of the surfaces from the midrib, being only slightly modified 

 by the elevation of the lateral branches. Intercellular spaces, 

 or net work, minutely capillary, as this tissue is developed from 

 the approximating and receding ridges of the sole. 



This species is dedicated to Mr. A. H. Worthen, State Geologist of Illinois, 

 whose indefatigable labors in the field, and whose zeal and devotion to the inte- 

 rests of science, promise a rich harvest to Western Geology, and through whose 

 kindness and liberality we have been permitted to describe this and the follow- 

 ing species of Polyzoa. 



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



COSCINIUM ELEGANS, Prout. 



PL 22, fig. 2. 

 Coscinium elegans, Prout, 1860. Proceed. St. Louis Acad, of Sci., vol. i, p. 572. 



Polyzoum a leaf-like expansion between what seems to be a 

 wide bifurcation of the midrib, rythmical dimples from each 

 branch pointing at first obliquely toward each other, meeting 

 irregularly toward the middle, and anastomosing towards the 

 superior border, which is reflected upon itself by compression. 

 Dimples small, sharp and pointed, sometimes long ; longitudi- 

 nally, or transversely, there are from five to six in a space of 

 twenty m m. Cells large, almost visible to the naked eye, 

 with two prominent rounded lips, on the border of the dimples 

 they seem larger, and give to it a notched appearance. 



Though the measurements in this species are very nearly the same as in C. 

 Keyserlingi, from the Keokuk group, we are inclined to refer it to a distinct 

 species, from the narrower, longer and more pointed dimples which are lanceo- 

 late, while in C. Keyserlingi they are broader and more oval; this, together 

 with the difference in the surface distribution of the dimples, will, it is believed, 

 warrant the distinction. 



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

 saw, Illinois. 



