Yol. 52.] STRATA BETWEEN THE KIMERLDGIAN AND APTIAN. 549 



the Ki meridian and the Upper Neocomian : and sometimes it 

 was held to be entirely Neocomian. Under these circumstances, it 

 appears to me advisable to avoid this term altogether, the more so 

 that all the beds heretofore included under it have now been 

 relegated to their natural place in the general classification, which 

 is the Upper Jurassic. It was for the above reason that I found 

 it necessary to introduce in my former work the provisional name 

 1 Serie Speetono-russe ' for the beds overlying the Kimeridgian 

 and terminating with the zone of Pohjptychites Keys&rlingi. (See 

 p. 532 in Bull. Soc. Imp. Nat. Mosc. n. s. vol. v. 1891, or 

 p. 174 sep. cop.) 



II. On the English and German Species of Aucella. 



The casts of the English specimens of Aucella to be described 

 were in part obtained by me during my visit to the Woodwardian 

 Museum at Cambridge in 1838, and in part were sent to me with 

 the ammonites described in my work on the Speeton fauna, through 

 the kindness of Prof. T. M c Kenny Hughes, E.R.S. The German 

 specimens and casts I owe to the kindness of Prof. A. von Koenen, 

 of Gottingen, of Hcrr 0. Weerth of Detmold, and of the Rev. 

 Pastor Denkmann of Salzgitter. 



The representatives of the genus Aucella have been found in 

 England at two different horizons. The lower of these is the Lower 

 Portlandian bituminous shale of Central England (Upper Kimeridge 

 shale of English geologists), from which have been obtained some 

 specimens of Aucella Pallasi now preserved in the Woodwardian 

 Museum. Two of these specimens are figured in my paper, ' Juras- 

 sique superieur et Cretace inferieur de la Russie et de l'Angle- 

 terre,' l and I have nothing further to add to my former description 

 of them. Those which occur at the higher horizon are dealt with 

 in the following notes. 



Aucella volgensis, Lahus., ' Ueber die russischen Aucellen,' Mem. du 

 Comite geologique, vol. viii. no. 1 ( 1888), p. 38, pi. iii. figs. 1-17. 



The English form (PI. XXVII. figs. 1 a, lb, Ic) corresponds 

 well with the characters of this species established on Russian 

 specimens, and from any large collection of such specimens it 

 is not difficult to pick out individuals in all respects similar to the 

 English form, so that it is impossible to doubt the identity of tho 

 Russian and English species. In Russia, Aucella volgensis is most 

 abundant in the zone of Ammonites stcnompltalus and A. Marcousanus 

 — that is, in the lowest zone of the boreal Neocomian. The English 

 specimen is preserved in the Woodwardian Museum at Cambridge. 

 It bears the old label ' Inoceramus imbricatits, Lower Greensand, 

 Donnington,' and its matrix shows that it has been obtained from 

 the Spilsby Sandstone. This form seems to exist also in Germany. 



1 Bull. Soc. Imp. Nat. Moscou, n. s. vol. iii. (1889) pi. iii. figs. 4 & 5, p. 106 

 (p. 48 iu sep. copy). 



