236 C. D. WALCOTT PKE-CAMBRIAN FOSSILIFEllOUS FORMATIONS 



The most interesting feature of the fauna is the occurrence of un- 

 doubted organic remains and the presence of a crustacean of a much 

 higher type than most })aleontologists would have predicted for this 

 horizon. 



HELMINTHOIDICHNITEH, FITCH 



Helminthoidichnites f neihartensis, sp. 



(Plate 24, figures 1, 2, 4.) 



This is a very narrow trail that may have been made by a slender 

 worm or a minute mollusk or crustacean. From the convolutions shown 

 on the upper portion of figures 2 and 4 (plate 24), the impression is given 

 that the animal moved very much as a small mollusk does when wan- 

 dering about on the mud at low tide. The numerous small, round, dark 

 spots gathered along the trails and scattered about on the surface of the 

 shale are probably small flattened concretions. The}'' suggest spores of 

 an alga in some specimens (figure 3), but in the great majorit}^ of in- 

 stances they are clearly of concretionary origin. 



Formation and localities yielding Helminthoidichnites. — Algonkian, Gi'ey- 

 son shales; Deep Creek canyon and Sawmill canyon. Belt mountains, 

 Montana. 



Helminthoidichnites ? spiralis, n. sp. 



(Plate 24, figures 5, 6.) 



These curious spiral trails occur in association with H f neihartensis 

 in Deep Creek canyon. All that is known of them is shown in the 

 figures. 



Helminthoidichnites meeki, n. sp. 



(Plate 24, figure 7.) 



This is a finely presented trail from the gray fissile shale in which 

 H. f spiralis occurs. It is pressed flat and resembles the smaller speci- 

 mens of H marinus from the Lower Cambrian slate of Granville, New 

 York.^' 



PLANOLITES, NICHOLSON 



Planolites corrugatus, n. sp. 



(Plate 24, figure 8.) 



lliis is the cast of a burrowing Avorm that shows corrugations or an- 

 nulations of nearly the same character as those oi Planolites anmdarius 



* Tenth Annual Report, U. S. Geol. Survey, 1891, pi. 62. 



