Silurian Ichnolites. 219 



Walker Mill Road, at an elevation of less than 100 feet .above low- 

 water mark at Cincinnati, in shales of the age of the Utica Slate. 



AsAPHoiDiCHNUs DYEKi, n. sp. (Plate XIII., fig. 1, natural size.) 



The tracks upon the left side (in the specimen illustrated, and in 

 all other specimens which have been observed), are placed somewhat 

 in advance of those upon the right side, and they are also more dis- 

 tinctly defined. Each track upon the left has four toes — the left 

 or outer toe is the longer and the right or interior toe the shorter. 

 The toes do not come together as in A. trijidus, but spring from a 

 wider foot. Some of the toe-tracks are more or less fringed, which I 

 attribute to the action of tlie water, though Mr. Dyer is impressed with 

 the idea that it may indicate hairy or spinous feet. The tracks made 

 b}^ the right feet are hardly definable, as in all our specimens the feet 

 seem to have dragged more or less upon this side. 



It may be that this species should be referred to another genus, but 

 after examining five slabs having the tracks upon them, I have con- 

 cluded to leave it in this genus, where it seems, at least, to have some 

 affinit3^ 



The species was collected by C. B. Dyer, Esq., on the Walker Mill 

 Road, in Cincinnati, and is from his collection. The specific name is 

 intended as a slight recognition of his many years of service to the 

 science. 



Trachomatichnus, n. gen. 



[Ety. — Trachoma, that whicli is made rough ; ichnos, a track.] 



This genus is proposed for the reception of the trails of molluscan 

 animals of an uncertain class, but possibly belonging to the Cephala- 

 poda. The reason for suggesting theCephalapoda is that the Orthoceras, 

 Endoceras, Cyrtocerns and Trocholites, which are found in these rocks, 

 were large enough to have made such trails, and we know of no genus 

 in any other class that seems to have been capable of making such. 

 The trail consists of numerous, simple or compound impressions, ar- 

 ranged in two series or rows which are separated by an intervening- 

 space of greater or less width. 



Trachomatichnus numerosus n. sp. (Plate XIII., figs. 2, 3 and 4.) 



In this species the width of a series or row is equal to or greater 

 than the distance between the two series which form the trail. The 



