218 



(Jincinnati Society of Natural History. 



haviiif^ no great depth, but where the water was almost motionless, 

 part of the time, and at other times ver^- slightl}' distuibed. The deli- 

 cately drifted sediment, and fine fucoidal trails, indicate the slightest 

 disturbance of the water ; Avhile the fine sediment of which the slat}- 

 shales is composed, and the preservation of the tracks indicate that 

 the weight of the animal pressed the feet into the sediment which re- 

 tained the impressions without disturbance from moving water until 

 they were filled by the slowly precipitated impalpable powder that fell 

 upon the bed of the sea. 



ASAPHOIDICHNUS TRIFIDU3, U. sp. 



In this species the anterior third of each track is 

 trifid, the outer toe usually branching from the main 

 stem of the track first, and the middle toe being a little 

 longer than either the outer or inner one. The illustra- 

 tion is from the Cin. Quar. Jour. Sci., as above stated, 

 but specimens better preserved have been collected by 

 Mr. Dyer, and show a small toe thrown off" from the pos- 

 terior elevation on the inner side of the track, having a 

 length about equal to the inner anterior toe. The 

 illustration represents the tracks of the right feet. 

 The difference in distance between the rows of tracks in 

 different specimens examined A'aries from 1^ to 3 inches, 

 and there is a corresponding difl^'erence in the size of the 

 tracks. The tracks are usually turned outward, but some 

 times the^' are directed straight in the line of the course 

 of the tracks; in the latter case they are more distant from 

 each other than in the former. The middle part of a 

 track is a simple elevated line. Tlie posterior part con- 

 sists of an elevation, with a toe upon the inner side as 

 above remarked. 



A well preserved track, in a specimen having a dis- 

 tance of 2 1-5 inches between the two rows, measured be- 

 tween the posterior part of the tracks, has the following 

 dimensions: Length, 0.52 inch; length of inner anterior 

 and posterior toe, each, 0.13 inch; length of outer pos- 

 terior toe, about the same; length of middle anterior toe, 

 0.15 inch. In a specimen having a distance of 1.5 inches 

 between the rows, a track has a length of 0.4:2 inch. 



'I'll is species was first collected by C. B. Dyer, on 



Asaphoulichnu.^ 

 trifidus. 



