64 PROCEEDINGS OF THE AMERICAN ACADEMY. 



7 or 8, individual tracks, the terra Protichnites be restricted. Logan's 

 Climactichnites wilsoni, six and a half inches wide and thirteen feet long, 

 also from the Potsdam sandstone, which Dana suggested may have been 

 made by a large trilobite,* seems to be such. There is an interrupted 

 median furrow ; the oblique furrows were probably made by the legs, 

 and the lateral furrow bounding the track is much like that made by the 

 cheeks or sides of the head of Limulus. 



We now come to similar but less comjjlex tracks described by O. C. 

 Marsh, f also from the Potsdam sandstone near Port Kent, N. Y. This 

 trail was about six feet long, and the tracks were separated from each 

 other " by a space of about one and three-fourths inches, and having an 

 extreme width between their outer edges of two and a half inches." In 

 this trail there is no median furrow, no lateral ridge, and here and there 

 are double tracks, as if they were footprints made by a second anterior 

 pair of feet. The track has a decided merostomatous appearance, but was 

 probably made by a trilobite, as there are no Limuloid merostomes known 

 to have existed in the Cambrian, and the track could scarcely have been 

 made by an Eurypterid. 



The next set of paleozoic trails are those described by Miller and 

 Dyer \ in 1878, in a fine hard shale of the Cincinnati's stage of the Ordo- 

 vician Period at Cincinnati. The originals are in the Museum of Com- 

 parative Zoology at Cambridge, Mass., aud I am indebted to Dr. R. T. 

 Jackson for the privilege of examining them. One of them is similar to 

 that described below from Providence, but the trail is twice as wide, and 

 the tracks not so wide. They were perhaps made by a trilobite ; there 

 is no median furrow, or lateral ridges. § 



The trails of Limulus j^olyphemus. — Figs. 1, 2 (one-third natural 

 size). The trail made by this merostome has been described and figured 

 by the late Sir J. W. Dawson in the Canadian Naturalist, VII. p. 271. 

 He gives three interesting figures of the trails left by a single small 

 Limulus four inches wide on a sandy shore. In each of his figures the 

 median furrow is distinct, but the lateral marks are furrows " with slight 

 ridges exterior to these," while my example left only a ridge. The 



* Manual of Geology, p. 189 (first? edition), Fig. 259. 



t Araer. Journ. Sc. and Arts, XLVIII. July, 1869. Plate. 



\ Journ. Cincinnati Natural History Society, 1878. 



§ The trails figured by Emmons (Agriculture of New York, I.) as Nereites jach- 

 soni pipgnus and loomisii, appear to be Annelid trails, and none of those figured by 

 James Hall (Paleontology of New York, II. Pis. 13-lG) seem to have been 

 made either by trilobites or merostomes. 



