P. E. Raymond — Seaside Notes. 113 



Trails in the P re-Cambrian. 



The proper recognition of the origin of trails is of par- 

 ticular importance in the case of Pre-Cambrian strata. 



The following have been described as trails of worms 

 by Walcott. 6 All were obtained from the Beltian of 

 Montana. 



Helmintlioidiclimtesf veihartensis Walcott was de- 

 scribed as the trail of a slender worm, a minute mollusk, 

 or a crustacean. "Walcott grouped this specimen with the 

 worms, but evidently rather favored its interpretation 

 as a mollusk, for he stated: "From the convolutions 

 shown on the upper portions of figures 2 and 4 (pi. 24) 

 the impression is given that the animal moved very much 

 as a small mollusk does when wandering about on the 

 mud at low tide." This view is the one shared by the 

 present writer, and since mollusca other than gastropoda 

 do not appear till very late in the Cambrian, it seems 

 probable that this trail was made by some kind of a snail. 



Helmintlioidichnites? spiralis Walcott has the spiral 

 form of a watch-spring and while it reveals no very con- 

 clusive evidence of its origin, is very likely organic, and 

 if so, was probably formed by a small gastropod, since 

 it lies entirely upon the surface of the layer, and is too 

 smoothly coiled to have been made by an annelid in 

 motion. 



Helminthoidicknites meeki Walcott is from 1.50 to 

 2.00 mm. in width, and is notable for its remarkably 

 symmetrical curves. It is not a furrow or ridge, but a 

 plane marking such as might have been made by a gas- 

 tropod crawling along and leaving a path of mucous 

 behind it. 



Planolites corrugatus Walcott was described as the 

 cast of a burrowing worm, but is more likely a burrow. 

 It appears to be 4 or 5 mm. in diameter, and along a part 

 of it the cast is annulated, suggesting the former occu- 

 pancy of a segmented worm. Such annulations are not, 

 however, due directly to the segmentation of the animal 

 which made them, but as an annelid eats its way through 

 the mud, the material passes through the body and fills 

 the tunnel behind, so that each segment of the fossil cor- 

 responds to a hitch forward, rather than to a portion of 

 the body. 



6 Bull. Geol. Soc. Am., vol. 10, pp. 236, 237, pi. 24, 1899. 



