152 The American Geologist. September, mhm 
the beds we are considering. They bave contributed only ;« 
small percentage of the bulk of the material making up the 
deposit. It must be said, however, that the paper under con- 
sideration has the further distinction of being the first to 
announce the presence of these interesting and curious struc- 
tures in the fossil condition. 
In Texas, professor Hill recognizes two chalk horizons, one 
in the Lower Cretaceous, the other in the upper series of the 
same system. We are only concerned here with the chalk of 
the Upper Cretaceous, for that alone corresponds in age t<> 
our Sioux river beds. That this formation abounds in Fo- 
raminifera such ns Textularia and Globigerina, and that it is 
in reality chalk, professor Hill urges with pertinent force in a 
number of publications:* and it is to the writings of Hill 
that professor Le Conte refers when be acknowledges the 
presence of true chalk in Texas. 
HilTs work on the geology of Arkansas! is the subject of 
an admirable review by professor Marcou,* in the course of 
which Marcou calls attention to his discovery of true <-lmlh- 
near Sioux City (Iowa) and in Nebraska in L863. Speaking 
of his paper on the Cretaceous formations in the vicinity of 
Sioux City, etc., read before the Geological Society of France 
in IS60, Marcou says : "I took the precaution to carry with 
me pieces of rough chalk taken near Sioux City, and I drew 
on the blackboard with them the three sections that accom- 
pany the paper." 
Prof. S. W. Williston, in 1890, announced that the chalk of 
Kansas '-appears to be wholly composed of organic forms very 
readily visible under a comparatively low power (a one-fifth 
or a one-sixth objective and a C eye-piece)^^ ,, The forms 
seen by professor Williston are the minute coccoliths and 
rhabdoliths which Dr. Dawson so well described in 1874. and 
*.\nn. Rep., Geol. Survey of Arkansas, Vol. u. for 1888. Check I.isi 
nf Invertebrate Fossils from Cretaceous Formations of Texas, 1889. An- 
notated Check List, etc., Bulletin No. 1, Geol. Survey of Texas, 1889. 
Foraminiferal Origin of certain Cretaceous Limestones, etc.. Am Ge- 
ologist, Sept., 1889. Ge#logy of parts of Texas, etc., Bulletin, Geol. 
Soc. Am.. March, 1894. 
I Report cited. 
f American Geologist, vol. rv, \>. :!">7. Dec. 1889. 
gChalk from the Niobrara Cretaceous of Kansas. Science, Vol.xvi, |> 
249, Oct.. 1890. 
