42 PROCEEDINGS OF THE ACADEMY OF [1887 



These two consolidated groups, together with the Dakota Group, 

 the separate identity of which all geologists have recognized, con- 

 stitute the western Cretaceous section of the foregoing table. 



The New Mexican Section of Prof. Newberry seems to be 

 practically identical with the western section of the foregoing 

 table. ^ He seems to indicate, however, that there is in that region 

 a blending of the Dakota Group with the next overlying forma- 

 tion. It may be noted also that at least one of the species Avhich 

 Mr. Meek describes in that report as coming from the middle 

 division of the New Mexican Section^ is now known to belong 

 to a lower horizon than that of the base of his section, namely, 

 to that of the Comanche division of the Texas section. 



Southward from Dakota and Montana I have never been able 

 to separate the equivalent of No. 4 from that of No. 5 of Meek 

 and Hayden's section, either stratigraphically or paleontologi- 

 cally. It is for this reason that I have referred all strata that 

 carry any of the fossils which they indicated as characterizing 

 either of those divisions to the Fox Hills' Group alone. On the 

 other hand, while Nos. 2 and 3 are so closely related to each 

 other paleontologically that they are now generally regarded as 

 constituting one natural group, an upper and a lower lithological 

 division of the same are quite as clearly recognizable in southern 

 Colorado and northern New Mexico as in the Upper Missouri 

 Kiver region. 



It is a significant fact that while the separate identity of the 

 Dakota group has been indicated by specific identity of plant 

 remains, which are found over a large region, as well as by 

 tratigraphical position, there is a marked difference in the char- 

 :acter of the invertebrate fossils from different localities. I refer 

 especially to those which Mr. Meek^ and myself* have published 

 as coming from strata of that group in Central Kansas, as com- 

 pared with the few which have been found in southeastern Dakota, 

 The Kansas forms are mainly or wholly of marine origin, but 

 they are such as may have lived in littoral waters; while those 

 of southeastern Dakota are of diflferent species, and indicate a 



1 Newberry's Geol. Rept. Expl. Exped. from Santa Fe to Junction of 

 Grand and Green Rivers, pp. 32, 121, 122. 

 ^ lb., p. 126, pi. i, figs. 7 a, b. 



3 Ann. Report U. S. Geol. Sur. Terr, for 1870, pp. 297, 301-313; Vol. IX 

 U. S. Geol. Sur. Terr., p. 24. 



4 Proc. U. S. National Museum, Vol. 2, pp. 295, 296, pi. 5. 



