3 
The Zemistephanus fauna is also in the lower part of the Yakoun 
formation. It includes the ammonoid genera, Zemistephanus and Kana- 
stephanus. The fauna is not known in the Fernie formation of the Rocky 
mountains or, at least, is not represented by these ammonoid genera in 
any fauna known from there. It is probably represented in the Tuxedni 
formation of Cook inlet, Alaska, where Stephanoceras richardsoni has been 
recorded; 1 the writer, however, has not examined specimens from Cook 
inlet. There is some resemblance to certain Pacific faunas, e.g. a Jurassic 
fauna of New Guinea which includes a species resembling a Zemistephanus 
(See under Zemistephanus). The import of these resemblances will be 
better known as studies progress. The Ze?nistephanus fauna is another 
fauna of early Middle Jurassic age and probably close in time to the Defonti- 
ceras fauna. 
From the Itinsaites fauna only the ammonoid Itinsaites is described 
in the following first section of the account of the Jurassic Ammonoidea. 
The fauna occurs in the Yakoun formation on the southernmost of the 
Channel islands and includes other ammonoids, pelecypods, etc. Of con- 
siderable interest is the presence of the seeds of cycads which must have 
drifted in from a nearby land area. The fauna is probably close, if not 
identical, in. age with the Zemistephanus and Defonticeras faunas. 
As the study of the Canadian Jurassic faunas proceeds it is evident 
that they are many in number, although they are for the most part frag- 
mentary and scattered geographically. They record the presence of seas on 
the western part of the continent from fairly early Jurassic to well on in the 
Upper Jurassic. The seas, from at least earliest Middle Jurassic to middle 
Upper Jurassic time, spread eastward to the site of the Canadian Rocky 
mountains and even farther eastward, but it is not known: (1) whether at 
any one time the Jurassic sea was essentially one body of water or a 
number of distinct yet connected bodies; (2) whether the sea or seaways 
were or were not comparatively persistent; (3) whether seas of successive 
stages occupied essentially the same or different sites. 2 The Canadian strata 
contain some genera and even species of European faunas, but also contain 
many genera not known outside of western North America, and this is also 
true of most of the species. It remains to be determined whether this very 
local appearance of the faunas will become less marked as progress is made 
in the study of the Pacific and other faunas. It is noted, in passing, that 
to date no ammonoids of the subfamily Sonnininae have been found asso- 
ciated with those of the families Stepheoceratidae and Sphaeroceratidae in 
Canadian Middle Inferior Oolite faunas. 
The thick accumulations of massive tuff and agglomerate in the 
Yakoun formation are of Middle Jurassic age. Some of this material 
must have accumulated quite rapidly and some, due to the filling in of the 
sea, may have been laid down subaerially, but it is not all of one date, for 
there is evidence of at least one decided halt in the deposition. By early 
Upper Jurassic time, the deposition of volcanic products had ceased, at 
least locally. It is not known whether volcanic accumulations were 
resumed in later Upper Jurassic time, for whatever later Jurassic deposits 
may have been present were removed by erosion before Albian or late 
Lower Cretaceous time. Certain analogies with the Jurassic deposits 
1 Martin, G, C.: U. S. Geol. Surv., Bull. 776, p. 142 (1926). 
* Trans. Hoy. Soc., Canada, 3rd ser., vol. 21, pp. 70-71 (1927). 
