8 GENERAL OBSERVATIONS. 



they may be regarded as adding considerable weight to the conclusions 

 drawn by the field-geologists from other data. As these plants were the 

 only recognizable species furnished by those strata, holding as the)* do so 

 important a stratigraphical position, I have added descriptions of them to 

 the others, although it was originally proposed that this report should be 

 confined to invertebrate fossils alone. The existence of strata of the 

 Primordial period at several localities in the Rocky Mountain region has 

 been heretofore announced by different explorers ; but the discoveries made 

 by the Explorations West of the One hundi-edth Meridian constitute a mate- 

 rial addition to our knowledge of the rocks of that period in the western 

 part of the continent. 



CANADIAN PERIOD. 



Small collections made at a few localities in the House range, Western 

 Utah, and in the Schell Creek range, Southeastern Nevada, I have referred 

 to the Canadian period. The collections are not only small, but they com- 

 prise in all only twelve species. A part of these, however, are regarded as 

 quite characteristic of the Quebec epoch of that period, to which I have 

 assigned them with very little hesitation. Small as they are, these collec- 

 tions present a much greater zoological diversity than those of the Primor- 

 dial period do, and there is not among them that preponderance of one 

 zoological type over the others that has been mentioned as occurring among 

 the collections of Primordial fossils, which consist very largely of Trilobites. 

 The subkingdoms Protozoa, Radiaia, IloUusca, and Articulata are all rep- 

 resented among the fossils referred to the Canadian period ; the species and 

 higher groups to which they belong being compactly shown in the syste- 

 matic table on a following page. Among the more important of the char- 

 acteristic foi-ms of this period contained in the collections, the species of 

 Phyllograptus deserves especial notice as being the first species of the genus 

 yet discovered in the Rocky Mountain region, and also because the genus 

 is regarded as peculiarly characteristic of the Quebec epoch. The discovery 

 of strata of this period in Nevada and Utah is important fi'om the fact that, 

 with the exception of Professor Bradley's discovery in Idaho, their existence 

 throughout the great Rocky Mountain region was heretofore unknown. 



