258 c. scHUCHEHT — moRrisox axd texdaguru formations 



"It is advisable to take note of the difference in British and Continental 

 usage of the term Oxfordian (Oxford). We use Oxfordian as a synonym for 

 Oxford Clay, which Continental writers usually call Callovian : they use 

 Oxfordian for the higher horizon Oxford Oolites, for which we employ the 

 term Corallian. I suggested a revision a few years ago to avoid this sort of 

 ambiguity. This may be put in tabular form thus : 



•■Old term.<i New terms Ammonites 



Portlaudian Portlandiau 



Kimmeridgi.-ui Kimmeridginn Amoeboceras 



Corallian Argovian Cardioceras 



Oxfordian Divesiau Quenstedtoceras 



Callovian Callovian Cosmoceras 



''The anunonites you have sent me look older than Ainoehoceras. I am not 

 prepared to differ with Haug about putting them in Quenstedtoceras, but I 

 have my suspicions. However, their general character seems to point to basal 

 Oxfordian in the Continental sense — that is, basal Corallian of the English 

 classification. They are of earlier type than Amcehoceras. 



"Taking what Stanton says about American formations, T am inclined to 

 suggest the following correlation : 



'•European classification American formations 



Portlaudian f^pper 



) Lower ^ Naknek 



I with 



f TTT\f»cii» I J 



Kimmeridgian, . . 



C Upper Aucella 



) Lower Mariposa 



Argovian (^pper 



) Lower ^ Naknek 



I with = Sundance 



Divesian l^pper J Cardioceras 



1 Lower 



Callovian l^pper 



) Lower Chinitna" 



As it is well known that the genera of reptiles are rather restricted in 

 geological range, it is well to see what they can teach in this connection. 

 In the Sundance occurs the ichthyosanrian Bapianodon, first described 

 by Marsh and admitted by Gilmore to be closely related to the English 

 Ophthalmosaurus of the Oxford Clay. Andrews^^ later reinvestigated 

 tliis genus and concluded that "the English and American species may 

 l^e regarded as belonging to a single genns, which must be called Ophthal- 

 mosaurus, that name having the priority.^' We may add that this reptile 



" C. W. Andrews: Cat, marine reptiles of the Oxford Clay. Brit. Mus. Nat. Hist., 

 part 1. 1910. 



