252 THE CANADIAN NATURALIST. [A^ol. Vll^ 



two geological periods, but complicated by a simultaneous cliaDge 

 over the area in question from marine to estuarine and fresh- 

 water conditions. It seems certain that the formation of lignites 

 began in the Rocky Mountain region before the salt waters had 

 entirely left the area, and consequently while forms generally 

 known as Cretaceous were still livinu; there. The evidence does 

 not appear to show that the Cretaceous species were of them- 

 selves becoming rapidly extinct, but that over the Western 

 region, now forming part of this continent, the physical condi- 

 tions changing drove the Cretaceous marine animals to other 

 regions, and it is impossible at present to tell how long they 

 may have endured in oceanic areas in other parts of the world.- 

 This being so, and in view of the evidence of the preponderant 

 animal and vegetable forms, it seems reasonable to take the well 

 marked base of the Lignite series as that of the lowest Tertiary^ 

 at least at present. The formation described belongs to this 

 lowest Tertiary, being in fact an extension of Hayden's Fort 

 Union groiq), and from analogy may be called Eocene. Judging 

 from Hayden's descriptions this Northern extension would ap- 

 pear to be richer in lignite beds than that portion represented 

 on the Missouri River, and therefore to show a tendency in the 

 lignites to increase in importance northwards as the}) do south- 

 wards of that region. 



NOTE ON THE OCCURRENCE OF FORAMINIFERA^ 

 COCCOLITHS, &c., IN THE CRETACEOUS ROCKS 

 OF MANITOBA. 



By G. M. Dawson, As. R. S. M., kc. 



A great portion of the Cretaceous division in England and on 

 the Continent of Europe, is composed of typical chalk, a sub- 

 stance which must have been formed in the tranquil depths of' 

 the ocean, far removed from land, as it contains but a very 

 small proportion of any earthy impurity. It consists in great 

 part of the calc;a*eous shells of Foraminifera, and the still more 

 minute calcareous bodies known as Coccoliths. The remains of 

 the larger Molluscs and of Echinoderms occur but rarely. The 

 American representative of this formation contains no beds of 

 true chalk, but is made up for the mof-t part of deposits of sand. 



