152 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DESCRIPTION OF PLATE 21 

 Annelid Trails on Greyson Shales 



PAGE 



H elminthoidichnites ? ncihartensis Walcott 98 



Fig. I. (Natural size.) Two nearly parallel trails, with many small, 

 dark, thin, flattened, usually circular concretions attached 

 to them. U. S. National Museum, Catalogue No. 33795. 



2. (Natural size.) 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 fig. 

 I. U. S. National Museum, Catalogue No. 33795. 



3. (About X 10.) Enlargements of one of the small disc-like 



concretions associated with figs, i and 2. U. S. National 

 Museum, Catalogue No. 33795. 



4. (Natural size.) Same as figs, i and 2, but with many convo- 



lutions. This form is less common than the straight and 

 partly curved trails shown by figs, i and 2. U. S. National 

 Museum, Catalogue No. 33795- 



Helminthoidichiiites f spiralis Walcott 98 



Figs. 5. 6. (Natural size.) Two figures illustrating the typical form 

 of trail made by this curious species. U. S. National 

 Museum, Catalogue No. 33794. 



H elminthoidichnites meeki Walcott 98 



Fig. 7. (Natural size.) Illustration of the type specimen of the species. 

 U. S. National Museum, Catalogue No. 2,2,79?>- 

 The specimens represented by figs. 1-7 are from the Algonkian : 

 Belt (Greyson shales) terrane ; Deep Creek Canyon and Sawmill 

 Canyon, Belt Mountains, Montana. 



Planolites corrugatus Walcott 98 



Fig. 8. (Natural size.) Exterior cast of the burrow made by medium- 

 sized annelid in siliceous mud now forming the shales car- 

 rying Beltina danai Walcott. U. S. National Museum, Cat- 

 logue No. 2,2,7^' 



Planolites superbus Walcott 98 



Fig. 9. (Natural size.) A portion of the cast of a long burrow oc- 

 curring in a sandy shale interbedded in the Beltina danai 

 shales. U. S. National Museum, Catalogue No. 2i2>797- 



The specimens represented by figs. 8 and 9 are from the Algon- 

 kian : Greyson shales; Sawmill Canyon, 4 miles (6.4 km.) above 

 NeJhart, Cascade County, Montana. 



This plate was published as plate 24, Bull. Geol. Soc. America, 

 Vol. 10, 1898, Walcott: Pre-Cambrian Fossiliferous Formations. 



