n 



1865, Trautschold* claims that A. Mosquensis is a Jurassic fossil, pos- 

 possibly of the horizon of the Kimmeridge clay, though in a paper 

 entitled '' Die Sehiedelinie Zwischen Jura utid Kreidc in Eussland,"y 

 dated 1875, the same writer is inclined to place it a little higher in tlie 

 series, and to make it of about the age of the Portland Oolite. A con- 

 clusion similar to the one last cited had been arrived at by Paidolph 

 Ludwig I in 18*74, who expressed the opinion that one of the varieties oi' 

 A. Mosquensis at least is a Tithonic form. 



Eichwald § thinks that Aucella Pallassii Keyserling, A. concentrica 

 Fischer, A. crassicoUis Keyserliug and A. Caucasia Von Buch, are onl}- 

 varieties of J.. 3Iosquensis based upon slight and unimjoortant differences 

 in sculpture and external shape. The correctness of this opinion has 

 not been disputed, but it is interesting to observe that while the surface 

 of the test of the whole of these nominal species is concentrically 

 striated, that of J.. Fallasii and A. Caucasia is marked also with more or 

 'less distinct radiating lines. 



In the "Proceedings of the Californian Academy of Sciences for 1864," 

 Mr. Cxabb described a fossil from the auriferous slates of the Sierra 

 Nevada, on the Mai-iposa estate, as Lima Eiringtoni. Mr. Meek || not 

 only I'egards this shell as an Aucella^ but says that it "i.s so nearly allied 

 to the A. Pallasii of Keyserliug," that he ■' would not be surprised if they 

 should prove to be identical when direct comparisons can be made." 

 The Californian shell has radiating as well as concentric stride. 



D'Orbigny and Eichwald have both noticed the remarkably close 

 resemblance wnich exists between casts of Aucella 3Iosquensis and 

 Inoceramus concentricus, and there is just the same similarity between 

 American examples of the latter shell and Aucella Piochii. It happens 

 that Inoceramus concentricus is rather abundant at the Queen Charlotte 

 Islands, also, that the specimens are onl}- well-preserved casts ; and it is 

 by no means easy to distinguish these from the Aucelloe from Tatlyaco 

 Lake. On the right valve of the casts of the Aucellae there is generally 

 an oblique aad deeply-channelled groove immediately under the beaks, 

 caused by the sitdden inflection of the valves at this point, and this is 

 always absent in the Inocerami. Still, it is scarcely possible to discrimi- 

 nate bet^Yeen casts of very young examples of the two species. 



* "Zeitschrift der Deutschen Geolog:isohen Gessellschaft, Berlin." Vol. XVI., pages 584 — 94, and Vol. 

 XVII., pages 448—456. 



t " Bulletin de la Societe Imp6riale des Naturalistes de Moscou." Vol. XLVIII., pa^'e 150. 



J Idem., Vol. XLVIII., pa^es 373-80. S " Lethea Rassica," Vol. II., page 523, 



II " Geology of California," Vol. I., pages 479-80. 



