PRIMORDIAL I-X)SSILS. 331 



proposed by Messrs. Meek and ITayden, as the fossils of two of the divisions 

 are found intermingling at the same place and in the same layers. The 

 specimens brouglit from the locality on Old Woman Fork of the Chey- 

 enne are of this character; and there seems to be the same trouble among 

 those from certain parts of lieaver Creek. The collection affords no speci- 

 mens belonging strictly to the Divisions No. 1 and No. 3, though the beds 

 were observed, but not collected from. 



SECTION II. 

 FOSSILS FROM THE PRIMORDIAL ROCKS. 



PLANTS. 



Genus PAL^OCHORDA. 



PAL^OCnORDA PRIMA. 



Plate 1, fig. 2. 



Palwochorda prima Whitf., Prelim. Rept. PaL Black Hills, 1877, p. 7. 



Plants, the remains of which, as preserved on the surface of the rock, 

 consist of narrow, linear, grass-like stipes, coiled or twisted without any 

 regular order, leaving by their removal or decomposition flattened depres- 

 sions of from one line to two lines in width and of an indefinite length, 

 with rounded or obtusely-pointed extremities. 



The examples in the collection before us are coiled, forming irregular 

 curves, usually enrolled, but sometimes sigmoidal. The surfaces are smooth 

 and structureless, presenting no marking whatever, although the substance 

 is usually of a somewhat lighter color than the surrounding rock. The ter- 

 minations are usually sharply rounded, and the whole appearance is more 

 that of the impression of an Annelid than of a plant ; though it is difficult 

 to conceive of the preservation of anything other than a plant to leave such 

 markings. We have referred them to the above genus, presuming them to 

 be congeneric with those figured by Professor McCoy in his Synopsis of 

 British Paleozoic Fossils, Plate 1 A, Fig. 3, although they are not elevated 

 or rounded bodies, but flattened stipes. 



