ADDITIONS AND CORRECTIONS. 353 



724. 2. CORNULITES (sp.?). 



Plate LXXXV. Figs. 13 - 16. 



The specimens here figured preserve the outer covering and surface marking in a very 

 good degree, and from this circumstance present some characters not usually observed in 

 species referred to this genus. The annulated character is less conspicuous, and in some 

 individuals scarcely an important feature. 



The specimens for the most part preserve some appearance of gentle annulations, which 

 are marked with conspicuous waving stria? crossed by finer longitudinal ones : the latter 

 are often partially or entirely obliterated. In addition to the annulations mentioned, the 

 surface often presents waved irregular elevations which leave the broader rings very 

 inconspicuous. 



In figs. 13 and 15, the limits of the successive rings, so well marked in the cast, are 

 scarcely visible ; while in 14 and 16, they become prominent : the latter figure is com- 

 pressed towards the larger extremity. 



Fig. 17 represents an enlargement of the longitudinal striae. 



One or two of these specimens are hollow ; preserving, within the thin striated co- 

 vering, a series of thick and strong annulations : they were originally hollow bodies, 

 apparently without septa or divisions of any kind. 



NOTE A. 



TRACKS OF GASTEROPODA AND CRUSTACEA IN THE CLINTON GROUP ( Pfig. 26 - 37) . 



Since this volume has been printed, I have had an opportunity of seeing many markings 

 of the kind described in these pages, together with others of different character. In the 

 summer of 1850, in company with Mr. J. D. Whitney of the U. S. Geological Survey of 

 the Lake Superior District, I traced the continuation of the Clinton and Niagara groups 

 northwestwardly along the shores of Lakes Huron and Michigan. There, on the peninsula 

 of Green Bay, markings of similar character were found upon the surfaces of arenaceous 

 layers of the Clinton group. Among these are two forms differing from any described in 

 this volume, as well as from each other*. One of these consists of simple parallel cutting 

 lines which are more deeply impressed at one extremity, and, continuing for a greater or 

 less distance, become gradually less deeply marked, and finally terminate, to be repeated 

 in the same direction over a considerable extent : these I have regarded as due to crus- 



• These I have described in the Report of Messrs. Foster and Whitney, U. S. Geologists of the Lake Superior 

 Land District. 



