LOWER CAMBRIAN, 63 
however, I think there is little doubt that they owe their origin to the trail- 
ing of algze over the bottom, especially in shallow water when the tide was 
running out. I recently made a study of the trails produced by algze on 
the flats of the inlet west of Noyes 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 alga. At other times, when 
from the action of the wind or any local obstruction the current was devi- 
ated, the most irregular and erratic trails frequently resulted. These obser- 
rations have led me to fully coneur with Dr. Nathorst, that Kophyton and 
many of the supposed fossil algze are casts of trails made by both vegetable 
and animal organisms. 
In order to place before American students illustrations of Kophyton, I 
have figured (on Pls. XXXII and XXXV-XXXVIII) specimens of the 
genus from the type locality at Lugnas, and also specimens of Kophyton 
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 
Kau Claire, Wisconsin (Pl. XXXYV, fig. 3). It differs in being larger and 
shorter; but this is probably an accident of origin, and not necessarily a 
genetic difference. On Pl. 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 Pl. XX XVII. 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 by the same agency, is shown by figs. 1 and 
2.0} Pl SOXOGVee 
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 Pls. XXXVI and XXXVII. They may 
have been so produced; but a comparison with photographs which I took 
the past season of trails made by drifting algze shows that the latter are 
also competent to produce such markings (Pl. XXXVI, figs. 1, 2). So far 
as known, no traces of medusze have been observed in association with 
the trails or markings illustrated, or with any known to me from American 
rocks. 
