NEW SPECIES OF CRETACEOUS INVERTEBRATES 
FROM NORTHERN COLORADO. 
By Junius Henperson, 
Curator of the Mluseum of the University of Colorado, Boulder 
In working over collections of fossils recently made in northern 
Colorado by expeditions from the University of Colorado several 
species were found which are new to science. The types have been 
presented to the United States National Museum, and they are here- 
inafter described. The Acanthoceras is frequently found in a frag- 
mentary condition at Left Hand Creek, a few miles north of Boulder, 
in the thin limestone bands which uniformly occur in the upper part 
of the Fort Benton shales along the base of the eastern Colorado 
foothills. The others came from the sandstone of Fossil Ridge, be- 
tween Loveland and Fort Collins, which appears to be a continuation 
of the Hygiene sandstone described by Doctor Fenneman, occupying 
a position at about the base of the middle third of the Fort Pierre 
shales. The fauna of this sandstone is highly interesting. It in- 
cludes about fifty species, quite a number of which have been re- 
ported from no other locality. Though the sandstone is so far down 
in the Pierre, a large proportion of the species are found also in the 
Fox Hills sandstones either in Colorado or in the upper Missouri 
and Yellowstone regions. A paper discussing this sandstone and its 
fauna has just been published.¢ 
ACANTHOCERAS COLORADOENSIS, new species. 
Ake XSGUOL tes, GIO) Il 
Shell discoidal; whorls convex, oblong in cross-section, their height 
greater than width; umbilicus well defined, about equal to the greater 
ciameter of the outer whorl; abdomen rounded, ornamented by two 
rows of sharp, longitudinally compressed nodes, each about midway 
between the medial line and the peripheral margin; each side of 
whorls ornamented by two other sets of nodes, one at the margin of 
the umbilicus, the other near the abdomen; nodes of all four sets con- 
nected by costee which nearly encircle the whorls, some curving 
shehtly but mostly passing somewhat forward in a straight diagonal 
“University of Colorado Studies, V. pp. 179-192. 
PROCEEDINGS U. S. NATIONAL MUSEUM, VOL. XXXIV—No. 1611. 
