436 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
corals (c) somewhat similar to Isastrea, and Thamnastrea sp. (r). 
Some other poorly preserved forms, apparently Bryozoa, are rather 
common. 
Pelecypods belonging apparently to the families Tellinidae (C), 
Pectinidae (C), Ostreidae (r), Pinnidae (r), and others. 
Gastropods probably of the families Naticidae (r), Capulidae 
(Platyceras, r), and others. 
Vegetation is present both as thin bands of carbonaceous material 
and as stem impressions. 
Conclusions as to Age. 
Since all species are new and the field relations obscure, for the 
region is one of great metamorphism, the determination of age must 
rest upon comparison with the nearest related species. This com- 
parison is summarized in the table on page 437. 
The closest comparison of species is thus with the uppermost 
Triassic (Rhaetic) and the Middle and Upper Jurassic. All of the 
Jurassic species, with one possible exception, show less primitive 
characteristics when compared with the Sutton species, or the Sutton 
species are more primitive, indicating an age prior to that of Middle 
and Upper Jurassic. All of the Rhaetic species are slightly more 
primitive than those from the Sutton formation, indicating for the 
latter less primitive forms a later period of development. This 
would place the age in the lower part of the Lower Jurassic, or Lower 
Lias. 
This fauna has apparently nothing in common with the Liassic 
faunas of Nevada, Oregon, and California noted by Hyatt. ^ The 
latter as noted by J. P. Smith - has no European relatives, except for 
the almost universal Arietites group, but is probably a northward 
extension of the South American type. The Sutton fauna, on the 
other hand, is rather closely related to the European and Indian 
faunas, and thus gives for North America a second type of Liassic 
fauna, though this Eurasian type has not yet been recognized from 
Alaska. 
1 A. Hyatt. Trias and .Tura in the Western States. Bull. Geol. Soc. Amer., 1894, 
vo!. .5, p. 395-434. 
2 J. P. Smith. Periodic Migrations between the Asiatic and the American Coasts- 
of the Pacific Ocean. Amer. Journ. Sci., ser. 4, 1904, vol. 17, p. 221. 
