166 Dr. Alexander Irving — The Trias of Devonshire. 



is the same association of inner and outer whorls at Headington^ 

 Malton, Pickering, and elsewhere, at least in different specimens. 

 The most perfect representation of this species is the figure given 

 by D'Orbigny under the name A. biplex on tab. 191, 192 of the 

 Terr. Jurassique, corresponding in every respect down to the smallest 

 size with ray own specimen.^ It corresponds also with the sutures 

 as drawn by Miss Healy, if these were taken from the opposite 

 side of the shell, were drawn in the usual manner with the lobes 

 pointing downwards, and shaded dark in contrast with the saddles. 

 The suture-line is rather remarkable for the breadth of the dorsal 

 saddle, and I doubt it would ever broaden out from such as 

 characterize A. pUcatilis of Sowerby, though we must allow some 

 liberty to the poor Ammonites while growing. 



As to the name that is to be applied to this fossil, I must leave 

 that to those who are more interested in the question, fur there is 

 plenty of choice. If we could be sure that Nautilus colahrinus of 

 Eeinecke, which came from Staflfelstein, had an old age like that of 

 ours, its name might be the earliest (1818) ; on the same condition 

 A. plauulatus of Schlotheim might be the next (1820). Sowerby's 

 name of biplex was the earliest English name (1821), but it included 

 only the earlier whorls. Am. instabilis of Phillips (1829-35) was 

 the next, but it was not very fully described and it was unaccompanied 

 by a figure.- Buckland in 183G gave the first complete description 

 and figure as A. varicostatus. D'Orbigny, in 184G (?), figured it as 

 A. biplex, but described it in the text as A. plicatilis ; and finally 

 Oppel in 1862 divided it and gave the name A. Martelli to the perfect 

 form. For myself I think that the use of Bucklaud's name, though 

 it has not the priority, would cause the least confusion, in which case 

 both of Sowerby's names might become obsolete, as ill-distinguished 

 and of doubtful reference. Possibly the object of nomenclature 

 may not be, after all, the establishment of the earliest and least 

 understood names, but the prevention of confusion as to what you 

 are talking about. 



IV. — Further Notes on the Trias of Devonshire, with speciai. 



REFERENCE TO THE DIVISIONAL LiNE BETWEEN THE BuNTER AND 

 THE KeUPER in THAT REGION. 



(Beply to some Criticisms by Mr. Alexander Soviervail.) 

 By Alexander Irvdcg, D.Sc, B.A. 



MR. ALEXANDER SOMERVAIL has been so good as to send 

 me lately a paper read by him before Section C of the British 

 Association at Southport, September, 1903, and printed in the 

 Geological Magazine, Dec. IV, Vol. X, No. 472, October, 1903. 

 The paper contains certain criticisms on the published work of 



1 It is marked as triplicate, but obviously it is usually biplicate. 



2 In 1874, iu the 3rd edition of the "Geology of Yorkshire," tliis name was 

 abandoned for Buckland's, reference being made to "pi. xiv, fig. 10," but the reference 

 is obviously to the " Geology of Oxford," where it is figured with Bucklaud's name- 

 in the legend. 



