Silurian IchnoUtes. 217 



SILURIAK IGIINOLTTES, WITH DEFINITIONS OF 

 NEW GENERA AND SPECIES. 



By S. A. Miller, Esq. 



We find drifted sedimentar}- lines and markings, the trails of fu- 

 coids, and the trails and tracks of mollusca and Crustacea well pre- 

 served, on the greenish-blue and bluish slaty shales of the age of the 

 Utica Slate, and upon the shales of what may be regarded as the pas- 

 sage beds from the Utica Slate to the Hudson River Group, at and 

 near the city of Cincinnati. The drifted lines and markings have 

 never been studied or illustrated. Some of them resemble the sche- 

 matical figni'es of the trails of drifting fucus, as described and illus 

 trated by the Swedish Geologist, Alfred Nathorst, in " Ofversigt af 

 Kongl. Vetenskaps-Akademiens Forhandlingar," 1873, pp. 25 to 52, pi. 

 15 to 17. And some of them may have been described, possibly, as 

 fucoids. 



No attempt has ever been made to describe the trails and tracks of 

 the mollusca and Crustacea found upon these rocks, with the exception 

 of an illustration by the author in the Cin. Quar. Jour. Sci., vol. i., p. 

 136, in 1874, which is reproduced in this article. It is absolutely ne- 

 cessary, in order to distinguish these impressions, in conversation or 

 in writing, that names should be applied to them, and I think, there- 

 fore, I may be excused for giving them generic and specific names, as 

 no harm can result from such a course. This has been done with suc- 

 cess in regard to the vertebrate tracks in more recent rocks, and I see 

 no insuperable objection to attempting it with the invertebrate trails 

 and tracks now under consideration. 



AsAPHoiDiCHNUs, n. gen. 



This genus consists of two rows of tracks; one representing the im- 

 pressions made by the feet upon the right side of the animal, and the 

 other the impressions made by the feet upon the left. The tracks are 

 separate and distinct, showing that the animal lifted its feet to ad- 

 vance, and appearing as if made by an articulated animal, but not by 

 one holding its feet in an inflexible position. The anterior part of 

 each track is divided and usually" thrown outward. The tracks follow 

 each other whether the course is direct or sinuous. 



By the generic name, I have intended to indicate that I am dealing 

 with such a track as I suppose an Asaphus may have made. 



I suppose these tracks may have been made at the bed of an ocean 



