134 GEOLOGY. 



has been sketched already. Very little is known of other forms of 



terrestrial life. 



The fresh-water fauna.— -The molluscan fauna of the inland waters 



had assumed a pronouncedly modern aspect as illustrated in Fig. 385. 



It had probably assumed consider- 

 able importance through the exten- 

 sion of the fresh waters, but the 

 record is by no means so ample as 

 would be expected if the deposits 

 were made mainly in lakes and river 

 , g-w-iz channels, and this is an additional 



Fig. 385.-Fresh-water fauna of the Co- reason for the growing opinion 



manchean (Lower Cretaceous) from that the terrestrial deposits were 



Montana (after Stanton). Pelecypoda: . l 



a, Unio farri Stanton; b, Unio douglassi in considerable part the products 



Stanton; Gastropoda: c, Viviparus f l anf ]_ was h n f fh P more trnn 



montanesis Stanton; d, Goniobosis (?) 0I ianQ WaSn 0I tne m0re tran 



ortmanni Stanton; e, Campeloma har- sient type, due to Overflows, 

 lovtitonensis Stanton. . , , . . ,_ 



storm- wash, sheet-wash, and other 

 forms of more strictly subaerial aggradation. 



The marine faunas. — There were two very distinct series of marine 

 faunas, implying two distinct maritime provinces — that of the Mexi- 

 can Gulf and that of the Pacific. The former had its connections east- 

 ward with Portugal and the Mediterranean region, the latter, north- 

 ward and westward with Asia and Russia. No species common to 

 the two provinces is known. The two faunas were not only distinct, 

 but were even contrasted in their generic aspects. 1 In the Gulf region, 

 Echinoidea (Fig. 386, a-c), Terebratulacea, Ostreidcc, Rudistce, Chamadce, 

 Cyprina, Protocardia, Cyprimeria, Naticidcc, Glauconia, Turritella (Fig. 



386, /), Nerinea, Hamites, Pachy discus, Schlcenbachia, Engonoceras, and 

 Turrilites are common, and some of them extremely abundant. But 

 half of the above genera and families are absent from the Pacific 

 province, the rest are rare or of local occurrence only, and always 

 represented by different species. On the other hand, in the Pacific 

 province, Aucella (Fig. 387, k, I, in), which is wholly absent from 

 the Gulf region, is extremely abundant in the Knoxville beds, 

 and Belemnites, Rhynchonella (Fig. 387, r), Crioceras, Anchyloceras. 

 Hoplites (Fig. 387, c), Phylloceras (Fig. 387, b), -and Lytoceras (Fig. 



387, a), are common, while rare or absent from the Gulf province. 



Stanton, Jour. Geol., Vol. V, 1897, p. 607. 



