GORHELATiON OF SUNDANCE AND MORRISON 257 



tains a fauna characterized by several species of Cadoceras, which has been 

 referred to the Callovian by Neumayr, Hyatt, and Pompeckj. Immediately 

 above the Chinitna is the Aucella-he'dYing Naknek formation, 5,000 feet thick, 

 in the lower 600 feet of which is a zone containing several forms of Cardioceras 

 so closely related to those found in the Sundance that I believe them to fur- 

 nish a good basis for approximate correlation. Now, if the Chinitna is Cal- 

 lovian, this lower part of the Naknek formation ought to be Oxfordian (and 

 possibly Corallian). ... On the best evidence we have, I think that the 

 Sundance formation is somewhat later, but not very much later than Callo- 

 vian." ' 



In a letter of February, 1917, Stanton remarks further as follows : 



"In the Mariposa formation of California there is Cardioceras duMuni Hyatt, 

 which earlier was referred to G. alter nans by J. P. Smith (Bulletin of the 

 Geological Society of America, volume 5, 1894, page 253), who pointed out the 

 differences between it and C. cordiforme. C. alternans is the genotype of 

 Amcehoceras and is characteristic of the Lower Kimmeridgian. This C. duMum 

 is probably of Lower Kimmeridge age and it is associated with Aucella. Now, 

 there is no Aucella fauna in the Sundance, and in view of the fact that Juras- 

 sic Aucellae are abundant in Alaska, Oregon, California, and Mexico, it seems 

 to me that their absence from the Sundance indicates that that formation was 

 not contemporaneous with the Aucella-hesirmg beds of the Mariposa and other 

 formations of the west coast, but older ; and the finding of Sundance types of 

 Cardioceras in the Cook Inlet region beneath the lowest Aucella beds there is 

 definite proof that this is so. {Cardioceras was found in the same formation 

 which contained Aucella higher up, but the two were not found associated.) 

 . . . Hyatt, Smith, Lappa rent, and Hang have all referred the Sundance to 

 the Oxfordian, basing their opinions on the character of the ammonites." 



In March, 1917, Stanton writes that his assistant. Doctor Eeeside, is 

 studying all of the American forms of Cardioceras and related genera, 

 and that he distinguishes a considerable number of forms, but does not 

 believe any of them to belong to the alternans group or the genus Amoe- 

 hoceras, other than those of the Mariposa slate of California. 



Under date of February 24, 1917, Prof. J. P. Smith said in a letter to 

 the writer : 



"I do not know the Sundance fauna at first hand, but only from Whitfield 

 and Hovey's paper on it. It has no aflSinities with our West Coast faunas and 

 it does not seem possible to connect it with anything in the Mariposa. I have 

 always been inclined to regard it as Oxford." 



The writer, thinking that the Morrison was of Comanchian age, and 

 that after all Cardioceras cord^iforme might be younger than Stanton's 

 determination, made inquiries of his friend. Dr. S. S. Buckman, of South - 

 field, England. To him he sent copies of the original descriptions and 

 figures, along with three good specimens of the Sundance ammonites. To 

 this inquiry came the following reply : 



