92 [Assembly 



markings. It is large, more ventricose, and very differently marked 

 from G. hilix, which occurs in the same formation. 



Geological formation and locality. In the shales of the Hudson-river 

 group : in Ohio and Tennessee. 



CYCLONEMA BILIX (Conrad). 



Since the preceding description was written, Mr. S. T. Carly 

 of Cincinnati has placed in my hands a series of specimens of 

 the above species ; or, inore properly, specimens which are 

 usually referred to C. hilix. These were collected at various 

 altitudes in the shaly limestone from the river level at Cincin- 

 nati, to beds which are 700 feet above that horizon. Although 

 I am able to indicate differences in the individuals, and those 

 from the greatest altitude present some marked peculiarities, still 

 I am at this time unable to point out characters which can be 

 relied upon for specific distinction. More extensive collections 

 may prove that there are three species w^ithin the vertical range 

 of 700 feet. A careful collection of these forms, whether they 

 may prove to be of distinct species or only varieties, will be of 

 great interest in showing the influence of time, and the gradual 

 changes which the ocean bed may have undergone during the long 

 period of quiet accumulation of seven hundred feet of fine sedi- 

 ments, every foot of which is filled with the remains of these 

 former creations. We are already aware that in the upper beds 

 of this extensive group, there is an accession of several species 

 of Brachiopoda which are unknown in the lower beds. 



