64 PROCEEDINGS OF TIIE AMERICAN ACADEMY. 



7 or 8, individual tracks, the term Protichnitea be restricted. Logan's 

 Climactichnitei wilsoni,&\x. and u half inches wide and thirteen feet long, 

 also from the Potsdam sandstone, which Dana suggested ma\ 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 complex tracks described by O. C. 

 Marsh, t 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 merostonies 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 J in 1878, in a fine hard shale of the Cincinnati's stage of the Ordo- 

 viciau Period at Cincinnati. The originals arc in the Museum of Com- 

 parative Zoology at Cambridge, Mass., and I am indebted to Dr. B. 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 polyphemus. — Figs. 1, 2 (one-third natural 

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

 by the late Sir .1. \V. Dawson in the Canadian Naturalist, VII. p. 271. 

 He li'ives three interesting figures of the trails left by a Bingle 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 Blight 

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



* Manual of Geology, p 189 i first i edition), Big 



t Amor. Journ. Be. and Arts, M.viil. July, 1869 Plate. 



I .luiirn. Cincinnati Natural Bistory Bociety, 18' 



§ The ir.iil- figured l>y Emmoni (Agriculture of New York, I.) as Iterates jack- 

 in : appear to be Annelid trails, and nunc of those figured by 



James Ball (Paleontology of New York, II. Pis. 18 16) seem t<> li:i\ <■ been 

 made either by trilobitei <>r merottom 



