242 W. N. LOGAN 
of opinion has as yet appeared in our geological literature. 
Among the lines of investigation which suggested themselves 
were the following: (1) The nature and extent of the interior 
Jurassic sea; (2) the relation of the interior fauna to other 
faunas; (3) the connection or connections of the sea with the 
ocean; and (4) the causes for the lack of communication 
between the Interior province and the Californian faunal prov- 
ince: ; 
Some of these questions, notably the second and fourth, have 
already received a somewhat exhaustive discussion at the hands 
of a number of geologists. In the majority of cases, however, 
the conclusions formed have been connected with certain funda- 
mental assumptions concerning the validity of which there is at 
present profound skepticism. As these new doctrines are more 
or less intimately associated with new fundamental hypotheses, 
a test of the one is in a measure a test of the other; but a dis- 
cussion of original postulates does not fall primarily within the 
province of this investigation. Therefore the discussion will pro- 
ceed along the lines already indicated and in the order above 
mentioned. 
Nature and extent of the sea.—I1n order to present the data 
upon which our conclusions concerning the nature and extent 
of the Jurassic sea are based it will be necessary to give a sum- 
mary of the stratigraphical and faunal conditions of the present 
known Jurassic areas. In collecting this data I have consulted 
the writings of a long list of geologists who have labored in this 
particular geological field.t | On the whole it may be said that 
the results obtained by these men are strikingly harmonious ; so 
that no grave difficulty should be met in any attempted logical 
interpretation of the facts. 
These Jurassic areas will be discussed in the order which fol- 
lows: (1) The South Central Wyoming area; (2) the Southeast- 
ern Idaho area; (3) the Northern Uinta area; (4) the Southern 
Uinta area; (5) the Southern Utah area; (6) the Black Hills area ; 
(7) the Montana area; (8) the Canadian area; (9) the Aleutian 
t For references see following discussion. 
