2 
corrections, the comparisons with foreign species, the generic assignments, 
and the correlations, may claim an accuracy, and carry a weight which 
they would not otherwise have. Mr. Buckman, however, must not be 
held personally responsible for any errors that may appear. 
The ammonoids described in the following first section on Jurassic 
Ammonoidea, are all from the Yakoun formation. They are listed in a 
general paper on the Jurassic faunas of western Canada , 1 where their 
stratigraphic position and correlation are given and their use in dating 
times of volcanic activity and other geological phenomena is demonstrated. 
The Seymourites fauna, in the upper part of the Yakoun formation, 
must have had a fairly wide distribution in northwestern North America, 
for it is present not only at Skidegate inlet, but also on Kananaskis river 
(south of Banff in the Rocky mountains), where it is represented in the 
Ferine formation by Seymourites mcevoyi , 2 and also, possibly, in the Chinitna 
shale of the east shore of Iniskin bay, Cook inlet, Alaska, where Kepplerites ? 
cf. K. loganianus (Whiteaves) has been recorded . 3 The distribution 
indicates a sea, or several connected seaways, extending, from Alaska 
probably, down the western margin of the continent at least as far south as 
Skidegate inlet and eastward at least as far as Kananaskis river in the 
Rocky mountains. The ends of fern and cycad fronds occur with the 
marine fossils and must have drifted in from a nearby land area. As the 
genera Seymourites and Yakounoceras are not known outside of these locali- 
ties, it is not safe to infer further extensions or connexions of this sea, 
although Toricelliceras, a member of the fauna, is in the European Jurassic. 
The affinities of this fauna are with those of late Macrocephalitan and of 
Proplanulitan age in the British Jurassic, and, therefore, it is of early 
Upper Jurassic time. The dating is based on the following resemblances: 
Skidegate Inlet 
England and Europe 
Seymourites 
Yakounoceras 
Galilaeites ? 
Toricelliceras 
Galilaeanus etc. Proplanulitan age 
Gowericeras etc. Proplanulitan age 
Galilaeites. Proplanulitan age 
Toricelliceras . Late Macrocephalitan age 
The Defonticeras fauna, in the lower part of the Yakoun formation, has 
not yet been found in the Fernie formation of the Rocky mountains, but 
possibly may be present in the Tuxedni formation of Cook inlet, Alaska, 
where Sphaeroceras oblatum and Sphaeroceras have been recorded 4 . The 
writer, however, has not examined any specimens from Alaska and cannot 
determine if the genus Defonticeras is present there. There is some resemb- 
lance to a South American fauna ( See under D. oblatum ), but, as far as 
known, the genus Defonticeras is not present in it. It is difficult, therefore, 
to determine the distribution of this fauna and to infer the extensions of 
the sea in which if lived. The nearest affinities of Defonticeras in the 
British Jurassic are with forms of late Sonninian or middle Bajocian age. 
The time, therefore, is early Middle Jurassic. 
1 McLearn, F. H.: “Some Canadian Jurassic Faunas”; Trans. Roy. Soc. Canada, 3rd ser., vol. 21, sec. IV, 
pp. 61-73, fig. 1, Plate I (1927). 
2 McLearn, F. H.: “New Jurassic Ammonoidea from the Fernie Formation, Alberta”; Geol. Surv., Canada, 
Bull. 49, PI. IV, figs. 1, 2 (1928). The generic name Seymourites takes precedence over Yakounites. 
* Martin, G. C.: U. S. Geol. Surv., Bull. 776, p. 165 (1926). 
* Martin, G. C.: U. 8. Geol. Surv., Bull. 776, p. 142 (1926). 
