Thompson: The Ammonites called A. serpentimis, 215 



up to be a thicker whorled, more strongly-cost at ed and more 

 widely umbilicated species than A. mulgravhis ; wherefore 

 though the two forms are evidently closely allied, I think it 

 desirable to retain the two names/* 



The above confirms my own work on the common Yorkshire 

 fossil, the result of which is, that the type described and figured 

 below is the adult of falcifer. 



The following extract from d'Orbignyf will give the history 

 of the names, and is that author's opinion on the matter : — 

 * Reinecke, en 1818, a decrit et figure cette esp^ce presque 

 adulte, sous le nom d'Argonauta serpentinus, et jeune sous 

 celui de Ccecilia, dont Schlotheim a fait, en 1820, les A. serpen- 

 tinus et capellinus. La meme annee, Sowerby appelait I'adulte 

 Strangewaysii, et le jeune Falcifer. Deux ans apres, de I'adulte 

 encore, Young et Birds, en 1822, faisaient leur A. Mulgravius. 

 II en resulte que I'espece a six noms distincts, dont le plus 

 ancien est Serpentinus, qu' on doit conserver ; ainsi les noms 

 de Cacilia, de capellinus, de Strangewaysii, de Falcifer et de 

 Mulgravius, employes quelquefois par les auteurs, doivent etre 

 renvoyes a la synonymic. 'J It appears from this extract that 

 d'Orbigny, following Schlotheim's description of what seems 

 to me to be an intermediate form, figured a specimen much 

 resembling mulgravius as serpentinus, and suppressed the Eng- 

 lish name. 



Bayle, Wright, Blake, and others, followed d'Orbigny. 

 Confusion arose in consequence, since we had so many names 

 attached at different times to one ammonite, which names 

 had really been given by their authors to various species. 



This is exceedingly strange, for Reinecke's figure is so clear 

 and he took the further trouble to give a section of his specimen ; 

 Young and Bird, also followed by Simpson, described mul- 

 gravius, one would think sufficiently well. 



The three ammonites under discussion are really unlike one 



* In Litt,, May 7th, 1909. 



t ' Terrain Jurassique,' t. I., p. 218. 



X [Translation — Reinecke in 18 18 described and figured this species, 

 almost adult, under the name of Argonauta serpentinus, and young, under 

 that of Ccecilia, from which Schlotheim in 1820 made A. serpentinus and 

 capellinus. In the same year Sowerby named the adult strangwaysii, 

 and the young form falcifer. Two years afterwards, from the adult again, 

 Young and Bird, in 1822, made their A. mulgravius. As a result of this 

 the species has six distinct names, the oldest of which is serpentinus, which 

 ought to be kept ; so that the names, CcBcilia, capellinus, strangwaysii, 

 falcifer and mulgravius, sometimes used by authors, ought to be relegated 

 to synonomy]. 



1909 June I. 



