W. Cross — Denver Tertiary Formation. 275 



cited, hint at airy peculiarity of the Table Mountain strata, nor 

 does he intimate in any way that they have been or might be 

 regarded by any one as belonging to a series different from the 

 coal-measure beds. 



d. The Invertebrate Fossils. 



A few invertebrate fossils have been found in the Denver 

 heds, all of them coming from a ravine by St. Luke's Hospital, 

 Highland (a suburb of Denver), where they were found by 

 Mr. T. W. Stanton, in association with fossil leaves and a small 

 tooth of a crocodile. The shells were submitted to Dr. C. A. 

 "White, of the U. S. Geological Survey, for determination, who 

 reports as follows concerning them : 



" The invertebrate fossils which have been collected from the 

 Denver Formation comprise five species. One of them is a 

 Unio, and another is a Physa, both too imperfect for specific 

 determination. Another is apparently a Corbicula. The other 

 two I have recognized as Viviparus trochiformis and Gonio- 

 basis tenuicarinata, respectively, of Meek and Hayden. 



"If these fossils had been submitted to me without any 

 statement of correlated facts, I should have hardly hesitated to 

 assign them to the Laramie Group, because the two last named 

 species are common and widely distributed in that Group and 

 forms similar to the other three are common in that Formation 

 also. 



" That Viviparus trochiformis and Ooniobasis tenuicarinata 

 may have survived from the Laramie epoch into that of the 

 Denver Formation is not at all improbable, especially in view of 

 the fact that I found both those species in Utah to have passed 

 up from the Laramie into the Eocene Wahsatch Group. 



" The TJnio and Physa are such forms as one might natu- 

 rally expect to find in such a deposit as is the Denver Forma- 

 tion, which was presumably a purely fresh-water one. In such 

 a deposit, however, one would hardly expect to find a Corbi- 

 cula, but I am not aware of any reason why we may not as- 

 sume that one of the many forms of that genus which are 

 found in the Laramie Group survived to the Denver epoch in 

 company with the two species mentioned. 



'* In short, I do not regard these invertebrate fossils as nec- 

 essarily presenting any evidence against your conclusion that 

 the Denver is a separate Formation from the Laramie." 



e. The Vertebrate Fossils. 



A number of isolated fossil bones have been found, both 



in the Willow Creek and in the Denver beds. These have 



Am. Jour. Sci— Third Series, Vol. XXXVII, No. 220.— Apeil, 1889. 

 18 



