LOWEE CAMBRIAN. 63 



however, T think there is little doubt that they owe their origin to the trail- 

 ing of algae over the bottom, especially in shallow water when the tide was 

 running out. 1 recently made a study of the trails produced by algae on 

 the flats of the inlet west of Xoyes Point, Rhode Island, and was surprised 

 at the close resemblance of those trails to the fossil trails. When the tide 

 was running out trails many feet in length were made in direct lines, with- 

 out a bend or interruption, by the drifting algae. At other times, when 

 from tlie action of the wind or any local obstruction the current was devi- 

 ated, the most irregular and erratic trails frequently resulted. These obser- 

 vations have led me to fully concur with Dr. Nathorst, that Eophyton and 

 many of the supposed fossil algae are easts of trails made by both vegetable 

 and animal organisms. 



In order to place before American students illustrations of Eophyton, I 

 have figured (on Pis. XXXII and XXXV-XXXVIII) specimens of the 

 genus from the type locality at Lugnas, and also specimens of Eophyton 

 and somewhat similar markings from the Cambrian rocks of various parts 

 of the United States. 



The most Eophyton-like trail is that from the St. Croix sandstone of 

 Eau Claire, Wisconsin (PL XXXV, tig. 3). It differs in being larger and 

 shorter; but this is probably an accident of origin, and not necessarily a 

 genetic difference. On PI. XXXVIII the broad, strongly striated trail sug- 

 gests the sweeping over the mud of the tentacles of a large medusa. Another 

 specimen from the same layers is shown by fig. 2 of PI. XXXVII. These 

 occur in the lower side of a thin layer of Middle Cambrian (Tonto) sandstone 

 in the Grand Canyon of the Colorado, Arizona. Another peculiar marking, 

 that may have been produced hv the same agency, is shown by figs. 1 and 

 2 of PI. XXXV. 



Dr. Nathorst has suggested that certain delicate linear markings may 

 have been made by the trailing tentacles of a medusa. Some of these from 

 American localities are shown on Pis. XXXVI and XXXVII. Tliey may 

 have been so produced; but a comparison with photographs which I took 

 the past season of trails made by drifting algae shows that the latter are 

 also competent to produce such markings (PI. XXXVI, figs. 1, 2). So far 

 as known, no traces of medusa 1 have been observed in association with 

 the trails or markings illustrated, or with any known to me from American 

 rocks 



