6 GEOLOGICAL SURVEY OF THE TERRITORIES. 
familiarity with the geology of that region would of itself incline me to 
refrain from questioning the correctness of his reference of these fossils 
to Cretaceous strata, notwithstanding their Paleozoic aspect; but, for- 
tunately, he has made such questioning impossible, by sending pieces 
of rock in which both the corals and well-known forms of Cretaceous 
mollusean shells are imbedded together. Besides this, I have myself 
visited that locality and made collections from its strata, some forms of 
which I recognize as of the same species as a part of those sent by Mr. 
Lakes. I also recognize the strata there as belonging to the lower por- 
tion of the Fox Hills Group of the Cretaceous series, as that group is 
developed in Colorado; and they are doubtless equivalent with a por- 
tion of the Fort Pierre Group, or Cretaceous No. 4, of the Upper Mis- 
souri River region. 
Remains of the Celenterata are exceedingly rare in all the Creta- 
ceous rocks of Western North America, and therefore the discovery in 
them of any coralline form is of more than ordinary interest ; but the 
interest concerning these two forms is greatly increased by their evident 
Paleozoic affinities. Being imbedded in sandstone, the condition of 
their preservation is not such as to give entirely satisfactory results 
from their study. I have therefore referred them provisionally to Pale- 
ozoic genera, because, in their visible characteristics, they correspond 
more nearly with those genera than with any others known to me. 
Prof. H. Alleyne Nicholson, of the University of St. Andrews, Scot- 
land, whose labors in the fossil Actinozoa and Polyzoa are so well known, 
has kindly examined specimens of both these forms at my solicitation, 
and to him I am indebted for valuable notes concerning them, from 
which J have drawn in the following remarks embraced in the deserip- 
tions of the species. 
Several years ago, while examining the conglomerate beds of the Da- 
kota Cretaceous Group in Western Iowa, I found among the pebbles, of 
which those beds are so largely composed, some fragments of Paleozoic 
corals. These coral-pebbles were water-worn like the others, and like 
them they were also siliceous. That region was traversed by the east- 
ern shore-line of the earlier intercontinental Cretaceous sea, the waters of 
swhich washed the whole series of Paleozoic strata there. The fossils of 
those strata, especially the corals of Devonian and Upper Silurian age, 
are often silicified, and they doubtless reached that condition before 
Cretaceous times. It is, therefore, easy to understand that the corais 
found in the pebble-beds referred to are really Paleozoic corals which 
were redeposited in Cretaceous strata, and not Cretaceous corals of 
Paleozoic types. 
The case, however, is quite different with the corals sent by Mr. Lakes 
from the Cretaceous strata of Northern Colorado. These corals are 
calcareous and not siliceous, and they are also comparatively fragile. 
hey present no appearance of having ever been water-worn, nor does 
the stratum in which they were found, an ordinary slightly calcareous 
and slightly muddy sandstone, contain any water-worn masses of any 
kind larger than the grains of coarse sand. We therefore necessarily 
reach the conclusion that these corals are really of Cretaceous age, 
although having so much the aspect of Paleozoic forms. 
I am indebted to the late Prof. B. F. Mudge for the types of two new 
forms from the Dakota Cretaceous of Kansas; and a very interesting part 
of the following described species have been received from the Cretaceous 
Strata of Texas, having been collected at different localities and for- 
warded by Mr. D., H. Walker, Mr. G. W. Marnoch, and Mr. 8. W. Black, 
