Vol. 60.] I'PPER JURASSIC AMMONITES. '!•> 



belongs to the description. On this principle British geologi — 

 have acted : but foreigners have been led by the figures. 



The reference of the type of Ammonites varioeostatvs to the 

 Ampthill Clay, which represents a Corallian horizon, seems to be 

 correct. It appears in fragments on that horizon at Shotover. and 

 a line specimen from Osmington was exhibited by the speaker. It 

 is the adult form of Am. plicaHUs (Sowerby's description). 



Mr. H. B. Woodward remarked on the importance of finding 

 these type-specimens and of figuring them by the aid of photography. 

 He observed that the complexities of modern nomenclature were a 

 great trouble to the student, as in some lately-published manuals 

 different generic (or subgeneric) names were used for the same 

 species. With field-experience, however, one might become 

 familiar with the many forms of each leading species and with 

 the horizons which they characterized ; and the safest plan seemed 

 to be to identify the fossils without naming them. 



Mr. E. T. Xewtox thought that the Eev. J. F. Blake's expla- 

 nations showed the desirability of publishing good figures and 

 descriptions of the obscure and little-known type-specimens which 

 formed the subject of the Authoress's paper. The plicatiloid 

 ammonites were avowedly a difficult group to deal with ; and a 

 full knowledge of the type-specimens was a necessary foundation to 

 work upon. 



Prof. Sollas remarked that he had listened with great pleasure 

 to the complimentary remarks on the work of the Authoress, and 

 regretted that she was not present to defend before the Society 

 her own position in the disputed matter of nomenclature. The 

 Bev. J. F. Blake's suggestion was certainly ingenious, and required 

 careful examination : but, whether well-founded or not, it had 

 always been customary to accept the evidence of so-called ' type'- 

 specimens as conclusive. The type in the Xatural History Museum 

 was named and figured as ' biplexj that in the Oxford University 

 Museum was named and figured as i plicatUis i ; so that, unless we 

 abandoned our usual methods, these must be accepted as the correct 

 designations of their respective forms. 



Postscript to the Discussion. 



[I am sure that Mr. Blake will be the first to abandon his in- 

 genious suggestion when he has seen both of the ' types ' in 

 question. Xo one familiar with the Corallian Beds of Dry Sandford 

 and Marcham can doubt which of the two came from there, and 

 which from the Drift. But, apart from this, it is impossible to 

 transpose Sowerby's descriptions, for a careful perusal of them 

 shows that he does not speak of Ammonites plicatilis in the plural. 

 The only suggestions of plurality are found in the mention of 

 two localities in this sentence : — 



'A sandy stratum, containing beds of sandy limestone, at Dry Sandf'jrdand 

 Marcham, N.W. of Abingdon, produces tins shell ' ; 



