334 Correlation of the Upper Cretaceous Formations 



nite faunas of the Monmouth and Fox Hills are very similar in both their 

 general and specific make-up. The group is represented in Maryland by 

 Sphenodiscus hiatus, Scaphites conradi, and Belemnitella americana.- 

 Sphenodiscus lobatus has a western analogue in 8. lenticularis, which is 

 so closely allied that they have been constantly confused in the synonymies. 

 Scaphites conradi occurs in the Fox Hills in its typical form together 

 with a couple of varieties. Belemnitella americana is represented in the 

 West by the closely related B. bulbosa. All of these forms, both the 

 western and the eastern, are restricted in their distribution to the 

 horizon which they characterize. All of the three Maryland species 

 are more or less widely distributed along the East Coast and Gulf and 

 have proved trustworthy time markers wherever they occur. Eutrephoceras 

 dekayi, though restricted to the Monmouth in Maryland, ranges more 

 widely in the Western Interior. There is also a general similarity in the 

 Pelecypods and Gastropods, although there are few identical species. The 

 Cucullasas, so prominent in the Monmouth faunas, have a goodly repre- 

 sentation in the Fox Hills. In fact, most of the taxodont groups, the 

 Nuculas, Yoldias, Ledas, Areas, and, in the Fox Hills, Glycymerides, are 

 abundantly represented both on the East Coast and in the Interior. The 

 Anomalodesmacea and Teleodesmacea, on the other hand, constitute 

 minor elements in both. In the univalves, the Opisthobranchs, Pyropses 

 and Pyrifusi stand out conspicuously in the Fox Hills as well as in the 

 Monmouth. Anchura is present in both, though less abundant than in 

 the earlier faunas. Twritella is curiously absent in the Western Interior 

 and the Naticoids relatively rare. All in all, however, physical conditions 

 in the Western Interior and on the East Coast were much more similar 

 and the consequent faunas more directly comparable during the Mon- 

 mouth than at any other horizon of the Upper Cretaceous. 



Along the Pacific Coast the Upper Cretaceous is represented by the 

 Chico series, which contains a littoral fauna that has been recognized 

 from the Yukon to Lower California. The general facies is Indo-Pacific 

 rather than Atlantic or even Interior, so that there is little evidence for 

 direct correlation with the Maryland series. Stanton 1 who has studied 



1 Stanton, 1909, Jour. Geol., vol. xvii, p. 419. 



