240 C. D. WALCOTT PRE-CAMBRIAN FOSSILIFEROUS FORMATIONS 



Plate 24. — Annelid Trails on Grayson Shales 

 HelmintJioidichnites f neihariensis 



Figure 1. — Two nearly parallel trails, with many small, dark, thin, flattened, 

 usually circular concretions attached to them. 



Figure 2. — Apparently a single trail made by the animal turning about and finally 

 returning nearly on the line of the first trail. There are not as many 

 concretions as in figure 1. 



Figure 3. — Enlargement of one of the small disc-like concretions associated with 

 figures 1 and 2. 



Figure 4. — Same as figures 1 and 2, but with many convolutions. This form is 

 less common than the straight and partially curved trails shown by 

 figures 1 and 2. 



Helminthoidichnites ? spiralis 



Figures 5, G. — Two figures illustrating the typical form of trail made by this curious 

 species. 



Helminthoidichniies meekii 



Figure 7. — Illustration of the type specimen of the species. 



Planolites corrugatus 



Figure 8. — Exterior cast of the burrow made by medium-size annelid in silicious 

 mud now forming the shales carrying Beltina danai. 



Planolites superbus 



Figure 9. — A portion of the cast of a long burrow occurring in a sandy shale inter- 

 bedded in the Beltina danai shales. 



