WILLISTON. | The Kansas Niobrara Cretaceous. QAD5 
fore been confounded with the Niobrara. Sironectes I believe to 
be a doubtful genus, and Holosaurus is not distinct from Platecarpus. 
The distribution of these genera is of some interest. In all my col- 
lections I have yet to learn of a single specimen of Clidastes being 
found in the Rudistes beds, or indeed anywhere save near the top of 
the formation. The other genera extend to within a hundred feet 
of the base of the Ornithostoma beds, and possibly lower down. An 
examination of more material may perhaps show a restricted range 
in the species. I need not call the attention of future collectors to 
the importance of locating the horizon of specimens more accurately 
than has been done heretofore. Of the Pterodactyls two genera and 
eight species have been ascribed to Kansas. In the examination of 
the extensive material in the University of Kansas I so far find evi- 
dence of but five species. The largest is Ornithostoma ingens, of 
which O. umbrosus is a synonym. This species measured in life 
eighteen and one half feet from tip to tip of wings. A restoration 
now completed will shortly be published. This species is by far the 
most common in the formation, and almost the only one that I have 
found far down in the deposits. This does not necessarily mean 
that the smaller species are later than the large one, but rather 
that the lower deposits mean a deeper sea and more remoteness of 
the shore line. Nyctodactylus has been found in the yellow chalk 
only. 
The turtles are especially characteristic of the uppermost de- 
posits. Near the upper part of the yellow chalk remains of various 
species are common; in the lower strata they are rarely or never 
found. 
The Plesiosaurs occur in about equal abundance throughout the 
deposits. They are at best comparatively rare, but are relatively far 
more abundant in the lower beds. 
Finally the toothed birds are, I believe, confined to the upper 
beds. The only possible exception is that of the type of Icthyornis 
which was found by Mudge near Bread-bowl mound in Rooks 
county. 
In general, vertebrate fossils of all kinds are far more abundant, 
at least ten times so, in the yellow beds than in the white beds 
