200 QUICKSILVKR DEPOSITS OF THE PACIFIC SLOPE. 



lively little reason to doubt that the specimens which have been found in 

 the Horsetown and Knoxville beds, respective!}-, and referred to Behmnites 

 impressus Gabb, are specifically identical. 



Comparinj^ the nineteen species of fossils now known to exist in the 

 Knoxville beds witli those from the Horsetown beds, or, in other words, 

 with all the other species which Gabb refers to the Shasta group,' it appears 

 that all except six of them are certainl\' different from any of the latter. 

 One of these six, the Ammointcs Xcirherryi I'!', offers only a mere suggestion 

 of identity ; four are probably, but not certainly, identical, namely, Am- 

 monites ramosm f , Pofam'nJcs diademaf, Lima sltaftfaetmsf , and BlujnclioneUa 



.'; and the specific identity of one, Bclemnitcs impressus, has been 



regarded as certain. Tlie fact that the Belemnites, as a rule, do not present 

 salient, or even satisfactory, features by which to determine specific differ- 

 ences, detracts somewhat from the certaint\- of the last identification. 



Dr. White's opinion that Aucella Erringtnmi and A Bioclni Gabb are 

 specificall}' identical has been formed after he had had better advantages 

 for investigating the subject than seem to have been enjoyed by any other 

 person who has written upon the paleontology of California. He has not 

 only examined the original types of those two form.s, but hundreds of other 

 specimens of A. Piochii from Gabb's original locality, as well as from other 

 places. Furthermore, we made a personal visit to the locality on the Mari- 

 posa estate where the type specimens of A. Erringtonii were obtained, and 

 collected better .'specimens of it from the auriferous slates there and in the 

 immediate neighborhood than had before been known. We also obtained 

 from the same slates fragments of an ammonite, some impressions of a 

 shell apparently the rjioladomi/a oyhkulafa of Gabb, others that represent a 

 species of the Pectinida^ (perhaps the AmtL^siwu aitrium of Meek), and still 

 others which are undeterminable. On adding to these the Belemnites pa- 

 C'ficus of Gabb, tlie fauna of the auriferous slates of the Mariposa estate 

 amounts to at least five species of mollusks. It is true that only the Aucella 

 has been satistactorily identified as occurring in both the auriferous slates^ 



'Geol. Survey California. PaUvontology, vol. 2, pp. •20a-2.">4. 



*Some of the specimeus found in the .-luriferoiis slates of the Mariposa estate show more or less 

 distinct, radiating; lines, and the same pecnliarity h.-is been observed among examples from the Knox- 

 ville beds, as well as among Russian and AK-xskan example.s. 



