202 Bulletin of Laboratories of Denison University [Voi. xi. 
hoped that the plates will prove useful for the determination of 
the rocks actually found in the field. Even though the engineer 
may lack the discriminating knowledge of the trained paleon- 
tologist he can in many cases satisfy himself of the position of 
a stratum by the simple- inspection of the plates while others 
may be induced to carry the study farther by recourse to the 
published reports. 
For the study of the upper Cretaceous as exposed in cen- 
tral New Mexico and Bernalillo county particularly the student 
will receive much assistance from “The Colorado Formation,” 
by T. W. Stanton in Bulletin number 106, Meek’s “Inverte- 
brate Paleontology of the Upper Missouri,” forming volume 
IX of Hayden’s survey, and White’s report in Vol. IV of the 
Survey West of the looth Meridian. 
Mollusca. 
Ostrea prudentia. White. 
A form resembling White’s figure is from the monocline 
north-east of Island Mesa and south-east of Prieta Mesa where 
it is associated with upper Fox Hills species. 
Ostrea sannionensis, White. 
This species occurs abundantly in the Punta de la Mesa 
sandstone and in some cases forms extensive layers in company 
with several other species. A form has been found with cru- 
ciate outline (see figure) due to the unusual development of the 
upper plicae but it is not thought necessary to institute a new 
name for it. 
Ostrea lugitbris, Conrad. 
The typical form is found in the cephalopod shales in Rio 
Puerco valley. It would seem that the evidence is now com- 
plete that this species should include both O. blackii and O. 
belliplicata which have been found in the Eagle Ford group of 
Texas. We have specimens of the larger form from Una de 
Gato east of the Sandia mountains in the uppermost Fox Hills 
strata, which closely resemble White’s figures of O. belliplicata. 
