AGE OF KNOXVILLE AND HORSETOWN BEDS. 205 



and with other fossils which are common in the Horsetown, though not found 

 exclusively in that group. 



Besides these well determined fossils a considerable number of others were 

 found which Dr. White cannot identify specifically with entire certainty. 

 The impression derived from the genera and from the specific analogies of 

 these specimens is to confirm the inference made from the determinable shells. 

 They are Eriphyla, possibly unbonata, Gabb ; Tessarolax distorta, Gabb, too 

 imperfect for positive identification ; Pholadomya, probably an undescribed 

 species; 0/)i6% similar in external aspect to 0. vanGoiiverensis,W\ute^\es; 

 Ehynchonella, probably undescribed : a curious, remarkably flat Ammonite, 

 seemingly undescribed ; and a cast of a Trigonia. 



Inferences from the Relations at Riddles. — The discovery of this fauna at the 

 moderate distance of about 200 miles from the California localities evidently 

 makes it possible to regard the Horsetown and Knoxville beds as contempo- 

 raneous. It does not follow immediately or of necessity that these groups 

 were coeval, for since Aucella is a shell of wide time-range its occurrence 

 alone does not prove that the Knoxville may not be middle Jurassic 

 although the Horsetown is Gault. But the California Aucella localities 

 are the most southerly of those known in the northern hemisphere, and as 

 the genus undoubtedly migrated southward they probably represent the 

 latest or nearly the latest period at which the form existed ; so that the 

 Knoxville locality might be regarded as of later date than the Kiddles 

 locality rather than earlier. Even were there no such guide to a probable 

 conclusion, there would be in the present state of knowledge no ground justi- 

 fying the separation of the Hoi'setowu beds from the Knoxville group be- 

 cause, as has been shown, the two faunas were contemporaneous in southern 

 Oregon. 



Confirmatory Evidence from Canada. — Further confirmation of this view 

 is obtained by a study of Professor Whiteaves' and Dr. G. M. Daw^son's 

 papers.* Dr. Dawson studied the stratigraphy of Queen Charlotte's islands 

 and found in the Cretaceous, coarse conglomerates underlain successively 

 by coal-bearing shales and sandstones, then agglomerates, and then again 

 sandstones. These are respectively his subdivisions, B, C, D, E. In the con- 

 glomerates he found only Behmnites. In the conglomerates at Kiddles, 

 Belemnites also occurs, and Mr. Brown found one specimen of Aucella in this 

 position.f In the subdivision C, which is of nearly the same lithological char- 

 acter as the rocks at Riddles, Dr. Dawson found Ammonites batesii, A. trasJcii, 

 Aucella, and Pleuromya Icevigata, all of which occur at Kiddles and all ex- 

 cepting Aucella also at Horsetown. He also found Ammonites stoliczkanus, 

 Gabb, and Ancyloceras remondi, Gabb, which belong to the Horsetown series. 



* Mesozoic Fossils, by J. F. Whiteaves, part III, 1884. 



tif.as I suspect, the conglomerates at Riddles are theequivalentsof those in the Queen Charlotte's 

 islands, the latter are also Gault and not Dakota, as has been inferred on stratigraphical grounds, 



XXXI— Bull. Geol. Soc. Am., Vol. 2, 1890. 



