FOSSILS OF GRAND CANYON SERIES 235 



terrane, Kwagunt valley, within the Grand canyon of the Colorado, in 

 Arizona. 



Some obscure forms. — In the first announcement of the discovery of fos- 

 sils mention was made of a pteropod allied to Hyolithes triangularis. A 

 careful study of the specimens throws so much doubt on this provisional 

 identification that I hesitate to make a positive identification. Had the 

 specimens been found in known Cambrian rocks I should not hesitate 

 to consider them as obscure specimens of Hyolithes. It is possible, how- 

 ever, that they are of mechanical origin (see plate 27, figure 11). 



In the gray limestone, about 150 feet above the Chuaria circularis, occur 

 what appear to be the obscure remains of a shell which, if seen in the 

 Cambrian, would be referred to the genus Acrothele (plate 27, figure 9). 

 Reference has also been made to a fragment of what appears to have been 

 the pleural lobe of a segment of a trilobite belonging to a genus allied to 

 one of the genera Obolella, Olenoides, or Paridoxides.* It is possible 

 that this is correct, but with the experience gained b}^ a study of the 

 pre-Cambrian fossils of the Belt terrane, I should now hesitate to refer 

 to the fragment as a portion of a trilobite. It is illustrated in plate 27, 

 figure 10. 



Dr Carl Wiman illustrates f some small disc-like bodies from the pre- 

 Cambrian shales of the Wisings group, which may or may not be of 

 organic origin. It is interesting to note their resemblance to Chuaria, 

 and the student should read Dr Wiman's description and examine the 

 illustrations when studying the problematical organisms of the pre-Cara- 

 brian rocks. 



3I0NTANA BELT TERRANE 



Fossils. — The fossils thus far discovered in the Belt terrane occur in the 

 Greyson shales, in a belt of calcareous shales about 100 feet above the 

 Newland limestone, at a horizon approximately 7,700 feet beneath the 

 summit of the Belt terrane at its maximum development. Indications 

 of fossils were first discovered near the mouth of Deep Creek canyon, a 

 short distance above Glen wood postoffice. Subsequently they were found 

 in Sawmill canyon, about 4 miles above Neihart. 



The fauna includes 4 species of annelid trails and a variety that ap- 

 pears to have been made by a minute mollusk or crustacean. There 

 also occur in the same shales thousands of fragments of one or more 

 genera of crustaceans. All the specimens are very much compressed and 

 flattened, and often large fragments of the test have been broken b}^ a 

 movement in the shale subsequent to their embedment in the mud. 



*Bull. U. S. Geol. Survey, no. .30, 1886, p. 43, par. 89. 

 t Bull. Geol. Inst. Upsala, no. 3, vol. ii, 1894. 



