L. F. Spatk — Notes on Ammonites. 171 



Wright 1 expressed the opinion that von Buch had considered the 

 suture-line of much greater importance than was justified by later 

 observations, and he stated : " In adult life, however, the form of the 

 suture-line is a valuable character." H. Douville, 3 ten years later, 

 took an exactly opposite view. He thought that the best family 

 characters would have to be furnished by the plan of the suture-line, 

 i.e., its general course in the post-gouiatitic stage before it was 

 masked by the complication of the lobes and saddles. Fischer, 3 on 

 the other hand, thought that "the suture-line was of real value for 

 classificatory purposes only when used in conjunction with other 

 characters of a ' higher ' order, such as the general form of the shell, 

 its ornament, mouth-border, or aptychus. If the suture-line were 

 the absolute basis for a classification of Ammonites, this would have 

 been accomplished long ago, since from von Buch's time onward all 

 palaeontologists had kept this character in view. Unfortunately no 

 one could affirm to-day that there exists a satisfactory classification 

 of this group of cephalopods ". 



Noetling 4 also thought that the systematic value of the suture- 

 line was not very great, since the protrusions of the visceral hump 

 that went into the lobes were of no importance. Opinions vaay differ 

 on this latter point, for in living animals even specific differences are 

 often very fundamental and extend to quite minor internal structures 

 or to the convolutions of the brain. 5 



It is not the writer's intention to give a complete history of the 

 alternate favouring and disfavouring of the suture-line as a basis for 

 the classification of Ammonoids, but it is surprising that, though 

 opinions on its value were freely given, little research as to the 

 nature and origin of the folded septal edge was carried on. It must 

 be admitted, however, that among modern workers on Ammonoids 

 many look upon the suture-line as the dominant feature, and Hyatt 6 

 even went so far as to say that " all classifications were necessarily 

 based upon sutural peculiarities". In view of the importance of 

 this statement it seems advisable to examine the other features of the 

 Ammonoid shell that have been used for classificatory purposes. 



With regard to the form of the shell and the coiling, their value 

 for a natural classification of Ammonoids is strictly limited. Few 

 authors would now group certain Inferior Oolite forms [Patoceras) 



1 Monograph of the Lias Ammonites, Pal. Soc. , 1880, p. 219. Only- 

 seven years after the compilation of Wright's work, hailed at the time of its 

 appearance as a "masterly monograph" (A. Geikie, Text-Book of Geology, 

 1882, p. 786), Professor Blake ("The Evolution and Classification of the 

 Cephalopoda, etc.": Proc. Geol. Assoc. , vol. xii, p. 292, 1892) had to say with 

 regard to the classification adopted by Wright, namely that of Neumayr, 

 originally published in 1875: "Its author, were he happily still with us, 

 would certainly regard it as quite inadequate and out of date at the present 

 time." 



2 " Sur la Classification des Ceratites de la Craie " : Bull. Soc. geol. 

 France, ser. Ill, vol. xviii, pp. 280, 291. 



s Discussion on above, ibid., pp. 291-2. 

 * Op. tit., 1905, pp. 59-60. 



5 A. v. Tschermak, " TJber d. Entwicklung d. Artbegriffs " : Tierarztl. 

 Zentralblatt(34), Vienna, 1911, pp. 351, 381. 



6 In Zittel-Eastman, Textbook of Palaeontology, 1st ed., vol. i, p. 546, 1900. 



