188 UNIVERSITY OF COLORADO STUDIES 
Inoceramus oblongus Meek 
This large shell, many examples measuring from eight to ten inches in length and 
six inches in breadth, is the most abundant species in the Hygiene beds from Lake 
Loveland to Rocky Ridge. Frequently a dozen are found in a single concretion. We 
have found a few just above and possibly in the Hygiene sandstone in the Boulder District, 
but by no means as robust as the more northern examples. It would be interesting to 
know the difference in conditions which made this species so abundant and large near 
Ft. Collins. It is enormously variable, particularly in the ratio of breadth to length. 
Our fine series passes by minute gradation from extremely compressed to highly inflated 
forms, the majority, however, being much inflated. Reported also from near Morrison, 
Colorado (White). We have no other records. 
Inoceramus sagensis Owen 
Quite common at Fossil Ridge and Rocky Ridge. We have found it in large numbers 
just above the Hygiene sandstone from three to eight miles north of Boulder and a few in 
that sandstone. Found in the Pierre of upper Missouri region (Meek). 
Inoceramus proximus ? Tuomey 
One specimen from Fossil Ridge is doubtfully referred to this species, and a few from 
above the Hygiene sandstone at Haystack Butte north of Boulder. Found in the lower 
Pierre of the upper Missouri region (Meek). 
Inoceramus vanuxemi M. and H. 
Recorded from Fossil Ridge by Dr. White and we have two or three specimens from 
there. It is very abundant in two or three thin calcareous sandy strata above the Hygiene 
sandstone three miles north of Boulder and we have seen one or two excellent specimens 
in that sandstone itself at Haystack Butte. Found in Pierre of upper Missouri region 
(Meek). 
Avicula linguiformis E. and S. 
Common at Fossil Ridge and a few found at Rocky Ridge. In the Denver Basin 
monograph this species is credited to the upper Fox Hills. In Dr. White’s list it appears 
as Pteria linguiformis. “Ranges through the Fort Pierre and Fox Hills Groups” in the 
upper Missouri region (Meek). 
Avicula nebrascana E. and S. 
We found one specimen at Fossil Ridge, a few above the Hygiene sandstone at the 
brick kiln near University Campus in Boulder and four miles north of Boulder, and a 
large number at the top of the Pierre shales four miles southeast of Windsor. Some of 
the early literature of western paleontology records this as Pteria nebrascana. Found 
in upper Pierre and Fox Hills in the upper Missouri region (Meek.) 
Ostrea inornata M. and H. 
We have one or two examples from Fossil Ridge. It is abundant just above the 
Hygiene sandstone from three to seven miles north of Boulder and west of Berthoud. 
In La Plata quadrangle it is reported from the upper Mancos formation, the probable 
equivalent of lower or middle Pierre. [Whitman Cross, Arthur Coe Spencer and Chester 
Wells Purington, La Plata Folio, Geologic Atlas of the United States, U. S. Geol. Sur., 
Fol. 60, p. 5, 1899.] Found in the upper Pierre of the upper Missouri River region (Meek). 
