Siluriun Icltnolites. 221 



form of the tracks, by the greater number iu each series, and by the 

 greater distance between the two series. It is distinguished from T. 

 numerosus by the greater distance between the series, by the less num- 

 ber of impressions in each series, and by the simple character of the 

 tracks instead of the compound or beaded form. 



I think the three species of tracks may be readily distinguished, and 

 yet they were likely made by animals closely allied, and belonging to the 

 same family, if not to the same genus. Different species of Orthoceras, 

 if thej^ ever made tracks upon the bed of an ocean, would probabl}' 

 make tracks as distinct from each other as these, aud possibly much 

 more distinct. 



Collected by (J. B. Dyer, in rocks of the age of the Utica slate, on 

 Walker Mill Road, in the City of Cincinnati. 



Teratichxus, n. gen. 



[Ety.— 7Vrrt.9, a wonder : ic/mos, a track or trace.] 



This genus is proposed for a singular trail, which we suppose ma}^ 

 have been made by some animal belonging to the class Cephalopoda. 

 It consists of numerous elongated more or less bifurcated impressions, 

 which are crowded together upon the right side and separated upon 

 the left. They are directed forward from the right side toward the 

 left, and may possibly be separable into two rows. 



Teratichxus coxfertds, n. sp. (Plate XIV., fig. 1, natural size.) 



This species is founded upon a single specimen. The impressions 

 of the trail are long, some of them are bifurcated; the}^ are crowded or 

 blended together upon the right side, and expanded or separated upon 

 the left. The impressions are directed forward from the right toward 

 the left side, though not continuous from one side to the other. They 

 are, however, so interlocked that they are not separable into two de- 

 finable rows. 



The illustration shows that the tracks after turning the arc of a 

 circle are blended or confused. Here we have the evidence that the 

 animal backed and changed its course. Beyond this the specimen pre- 

 serves onl^' part of the trail. 



Collected b}" C. B. Dyer, Esq., in rocks. of the age of the Utica Slate, 

 on Walker Mill Road, in Cincinnati. 



Petalichnus, u. gen. 



[Ety. — Petalos, spread out ; ichiios, a track.] 



This genus is also proposed for the reception of trails that may, pos- 



