260 



Meek's principal argument in favour of regarding the Dakota and 

 Utah rocks as Jurassic is thus stated in that report of Dr. Hayden's to 

 which reference has already been made. " The organic remains found 

 in these series present, both individually and as a group, very close 

 affinities to those in the Jurassic epoch in the Old World ; so close 

 indeed, that in some instances, after the most careful comparisons with 

 figures and descriptions, we are left in doubt whether they should be 

 regarded as distinct species, or as varieties of well known European 

 Jurassic forms. Among those so very closely allied to foreign Jurassic 

 species may be mentioned an Ammonite we have described under the 

 name of A. cordiformis, which we now regard as probably identical 

 with A. cordatus, of Sowerby ; a Grryphoea we have been only able to 

 distinguish as a variety from Gr. calceola, Quenstedt ; a Pecten, scarcely 

 distinguishable from P. lens, Sowerby ; a Mbdiola, very closely allied 

 to M. cancellata, of Goldfuss ; a Belemnite, agreeing very well with B. 

 excentricus, Blainville, &c." 



The strongest point in this argument is the fact first adduced, 

 namely, the occurrence in the rocks in question of an Ammonite (A. 

 cordiformis of Meek and Hayden) which seems to be an Amaltheus 

 or a Cardioceras, and in either case is a species which is very closely 

 related to the Ammonites cordatus of Sowerby from the European 

 Jurassic. But, on the other hand, associated with purely Cretaceous 

 types, the Lower Shales of Skidegate Inlet contain no less than four 

 species of Ammonites which if submitted to any European palaeontolo- 

 gist who had made a special study of the group, without shewing him 

 any other fossils from the same rocks, would almost certainly be re- 

 garded as Jurassic. These are Ammonites Michardsoni, Whiteaves, which 

 is a very typical representative of the Coronarii of Yon Buch, and which 

 therefore is probably a Stephana ceras : Stephanoceras oblatum and S. 

 cepoides, whose relations to the Jurassic Macrocephali have been pointed 

 out on pages 29, 30, 209 and 210 of the present volume -; and Peris- 

 phinctes Skidegatensis, Whiteaves, which as Mr. E. Billings suggested, 

 (on page 72 of the Eeport of Progress of the Geological Survey of 

 Canada for 1872-73) is of the type of P. tyrannus, Neumayr, from the 

 " Macrocephalen Kalken" of Brielthal. 



In regard to the G-ryphoea Nebrascensis, which Mr. Meek thought was 

 possibly a variety of Gr. calceola, Quenstedt, the specimens from Skide- 

 gate Inlet shew that the irregular radiating striae on the umbonal 

 region of the convex valve are as often absent as present, and apart 

 from this character it is difficult to see how the shells represented by 

 Meek's woodcuts of G-. Nebrascensis in the " Palaeontology of the 

 Upper Missouri " can be distinguished from the Gr. vesiculosa of 

 Sowerby as figured by Pictet and Campich^. 



