224 L. F. Spath — Notes on Ammonites. 



grouping by vonBuch iuto the three sections of Goniatites, Ceratites, 

 and Ammonites, or, by Wright, into three corresponding families. 

 As the discovery of rich Triassic faunse showed the impossibility of 

 separating the Ceratites from the Ammonites, so the interesting 

 Permian forms dealt the death-stroke to the division into Ammonitids 

 and Goniatitids. Professor Haug 1 stated already in 1894 that 

 " a classification of Ammonoidea iuto Goniatites and Ammonitids, or 

 into Petrosiphonates and Prosiphonates, would not be really natural, 

 except if all were descended from a single Goniatite family. 

 Permian Ammonites showed, however, that several families were 

 evolved, more or less in a parallel mariner, and passed through the 

 Goniatite into the Ammonite stage ". Thus, complication of the 

 suture-line, change of the protoconch from latisellate to angustisellate, 

 and modification of the septal necks took place in the different stocks 

 of " Goniatites" that persisted into the Permian and Triassic periods, 

 at different times; and since it is possible that the Goniatites 

 themselves did not originate from one single Nautiloid stock (for in 

 the Devonian several very distinct groups can be recognized) it is 

 clear that the subdivision of Ammonoidea into Goniatites and 

 Ammonitids cannot be upheld. 



Haug, in his admirable textbook, 2 indeed, divides the Ammonoidea 

 from the Devonian onwards into several great "phyla": 

 Anarcestidse and Glyphioceratidae (the latter with many Triassic 

 families), Agoniatitidse, Prolecanitidse (with Ceratitidse), and 

 Gephyroceratidse. This last " phylum " includes the Phylloceratidse 

 and is therefore the root-stock of the host of the Jurassic and 

 Cretaceous Ammonites. The writer 3 had to differ from Haug on 

 this latter point and also from that author's interpretation of the 

 genera JVomismoceras, Dimorphoceras, and Thalassocerasf and there 

 can be no doubt that a good deal of research is necessary yet before 

 this classification of Haug's can be said to rest on a secure 

 foundation; but it marks a splendid advance in the right direction. 

 The same cannot be said for the three "phyla" Belocerata, 

 Tomocerata, and Gephyrocerata, proposed in his work on the Triassic 

 of Albania by G. v. Arthaber. 5 These "phyla", widely separated 

 already in the Devonian, are "assemblages of heterogeneous 

 ■elements", as Diener 6 has already pointed out, and show the 

 greater value, for classification of the larger groups, of the suture- 

 line compared with other characters. 



The Liassic and later families of Ammonites are then looked upon, 

 not as being subordinate to a sub-order " Ammonitidae " of the 

 order Ammonoidea, but as being, with some Triassic groups, 



1 " Les Ammonites du Permien et du Trias": Bull. Soc. Geol. France, 

 ser. in, vol. xxii, p. 386. 



2 TraiU de Giologie, vol. ii, fasc. 1, 2, Paris, 1908-11. 



3 Op. cit., 1914, p. 353. 



4 Op. cit., vol. ii, fasc. 1, pp. 754-5. 



5 Beitr. z. Geol. u. Palaeont. v. Oesterr.-Ung., etc., vol. xxiv, 1911. 



6 Triassic Faunce of Kashmir (Mem. Geol. Surv. India), N.S., vol. v, i, p. 3, 

 1913. 



