32 Tlte American Geologist. .luiy, i89i 
No. 1 is a veiT large leaf with obtuse teeth ; it measures eight 
and a half inches in lireadth. No. 5 might be referred to Grevi- 
opsis popuUfolia Ward, as well as to the species to ^vhich it is 
here assigned ; and, indeed, the generic and specific distinctness 
of these forms seems doubtful. No. 6 is an ovate-cuneate form 
which bears no small resemblance to two somewhat larger leaves 
in the museum of "Washburn College from alleged Laramie beds 
at Trinidad, Colorado. The identity of No. 7 with the species 
which "Ward has described from the white marl bed forming the 
summit of the "Foi*t Union" beds of Seven-Mile creek, Montana, 
under the name of Credneria daturce/olio, admits of no question, 
whatever doubt may exist as to the proprietv of referring the 
species to the genus Credneria. 
The occurrence of this species in the Loup Fork Tertiar}' is of 
unusual interest In "\^olume I. of ttie Fortieth Parallel Reports, 
published in 1878, King wrote, "I apprehend that the plant hori- 
zon at Fort Union will be found to be nothing but the northward 
extension of the "White River Miocene. " "VN^hatever be the age 
of the lower part of the Seven-Mile creek beds, the occurrence of 
Credneria datnrcefolia in the Loup Fork indicates not onl}' that 
the white marl cliff which forms the summits of those beds is 
probabl}' referable to an epoch not earlier than that indicated by 
King, but that it may well be reexamined with a view to its pos- 
sible referability to the Loup Fork. 
A curious palaeoutological feature of the Alpine chalk-marls is 
the apparent evidence of a certain degi'ee of brackishness in the 
waters of the great lake. 
Following are the names of the diatoms identified by Rev. Fran- 
cis Wolle, of Bethlehem, Pa., in a sample of the marls sent him. 
together with his notes on the habitats : 
Cymhelhi cistula Hempr. — More frequently fresh-water than brackish. 
Navicula peregrina. — Brackish water. 
" tenelln Breb. ) These two may be forms of Schizonema\ 
" lanccolata Ktz. ^ hence marine. 
Cosclnodiftcus looodicardi Eilenstein. — This is the most decidely ma- 
rine. 
Mchixira (jranulata (p]hr.) Kalfs. — Brackish or marine water. 
The Loup Fork calcareous sandstone has been universally called 
a fresh-water deposit. This view is no doubt essentiall}' correct ; 
yet the intiuence of the g3i3siferous and saliferous ''red-beds'* 
rtoor of the Indian Territor}- district of the lake ma}- have im- 
parted locally a somewhat brackish character to the lake-water. 
