98 UNIVERSITY OF COLORADO STUDIES 



FT. BENTON 



Cephalopoda. — Three imperfect casts found five miles north of 

 Boulder in general outline resemble the Placenticeras group of Pseudo- 

 ceratites, but, as they are not well enough preserved to show the surface 

 ornamentation or sutures, and it cannot be even definitely ascertained 

 whether the keel which characterizes some other groups is absent, 

 more and better material must be awaited. 



Another series, collected north of Left Hand Creek by Professor 

 R. D. George, Professor D. W. Spangler, Mr. F. M. Dille, and the 

 writer, with the surface ornamentation better preserved, appear to be of 

 different species, resembling Placenticeras in the row of nodes near 

 the umbilicus, another row near the ventro-lateral angle, another at 

 the ventro-lateral angle, and in the absence of a keel, but apparently 

 differing in other important respects. The specimens are inner volu- 

 tions, except two large fragments which may be body chambers of the 

 same species, none of them showing traceable sutures. The unidenti- 

 fied specimens of this series include at least two species. Two other frag- 

 ments seem to answer to the description of Helicoceras ? corrugatum. 



Inoceramus labiatus. — At various points north of the city occurs this 

 species in abundance, quite variable in form, as usual with the genus. 



Inoceramus sp. — An undetermined and perhaps undescribed species 

 has been found in this formation at the mouth of Bear Canon, as well 

 as north of Boulder. The specimens are quite flat, which may possibly 

 be the result of pressure, and are all in a fragmentary condition. 



Anisomyon ? sp. — Professor Spangler has found one specimen north 

 of Left Hand Creek which seems to be closely related to Anisomyon. 



Veniella mortoni. — One or two specimens seemingly referable to this 

 species were found north of Left Hand Creek. 



Ostrea sp. undescribed. — An oyster pronounced by Dr. Stanton an 

 undescribed species is found in great quantities in a narrow zone in the 

 lower third of the formation, in such fragmentary condition that they 

 cannot be satisfactorily described or figured. 



Ostrea sp. — An undetermined species, probably of Ostrea, occurs 

 wherever Inoceramus labiatus is found in this region, always in the 

 form of poorly preserved rusty casts. This species, with I. labiatus 



