342 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



The upper part of the section on the South Branch, con- 

 taining concretions full of Avicula Nebrascana, is doubt- - 

 less the representative of No. 5 in this region. 



[Several of the specimens obtained near Sand Hill Lake 

 on Qu'appelle Eiver, and the South Branch of the Sas- 

 katchewan, are from a green sandstone, which is more 

 indurated, but in other respects more like the green sands 

 of New Jersey, than any I have before seen from north- 

 western localities. In some of these, there are great 

 numbers of Avicula linguceformis and A. Nebrascana, 

 the first of which occurs in both Nos. 4 and 5 of the 

 Nebraska section, but is more abundant in the latter ; and 

 the other is nearly or quite restricted to No. 5, where the 

 two formations are not blended as is sometimes the case. 

 As this rock differs entirely in its lithological characters 

 from Formation No. 4, — while No. 5 is often highly 

 arenaceous, and sometimes assumes a slight greenish tinge, 

 at the higher northern localities in the Upper Missouri 

 country, — the probability is that it represents No. 5, or 

 the most recent member of the Cretaceous Series of the 

 north-west.] 



Among the specimens procured from the South Branch 

 were Scaphites Conradi, Nautilus Dekayi, Avicula lin- 

 guwformis, Avicula Nebrascana, Rostellaria Americana. 



Avicula Linguwformis. 



An imperfect specimen of this species. The lines represent shading. 



[Avicula linguwformis, Evans and Shumard, Proceed. 

 Acad. Nat. Sci. Phila., vol. vii. p. 163. 



