(iLYl'illOCEKATID.E. 57 



Middle Devonian. He admitted the near relationship between the two 

 g-enera, bnt considered Prionoceras as the link between the snpj)Osed radicle 

 Bniiicoceras and GUipkioccras. The genealogy of the Glyphioceratid^e, 

 according to Hyatt, is as follows: 



I Prionoceras -i-Glyphiocc'ras. 

 Muensterot'erai^-^Oastri(K•(^rat^^-Paralegoceras. 

 Dimeroceras-i-Pericyclus. 



Prof. K. A. von Zittel"has recently merged Vrionoceras in Brancoceras, 

 not even giving subgeneric rank to the former. Bnt even though the}^ may 

 be nearly related, their phylogeny justifies the separation. Both genera 

 probably branched off about tlie same time from I'arodoceras or from 

 Sporadoceras in the Upper Devonian, but Ar/anides (^Brancoceras) is not the 

 radicle, at least of the main branch, of the Glyphioceratidse. While it is 

 possible, although not known, that Mueiisferoceras may go through a Bran- 

 coceras stage, Prionoceras does not, neither does GUjphiocerds, nor Goniatttes 

 s. str. Prionoceras seems to have come directly from Parodoceras, and in 

 turn gave rise to Glyphioceras. It seems likely, too, that some species of 

 Gastrioceras descended directl}^ froni Prionoceras by division of the ventral- 

 lobe, while others may have come from Glyphioceras. In any case, whether 

 it came off from the radicle, or through Ghipkioceras, Gastrioceras is a later 

 branch than Glyphioceras, having its maximuni in the Upper Coal Measures; 

 it therefore deserves to rank as an independent genus. It also seems jjroper 

 to YQiixiw Prionoceras f , Aganides (Brancoceras'), and Muensteroceras, with full 

 genei'ic rank. 



Freeh'' derives the Glyphioceratidge from Sj^oradoceras, Ijut this 

 hypothesis is not in harmony with the ontogeny of Goniatites and Glyp)Mo- 

 ceras. However, too little is known of the development of these forms to 

 warrant any positive statement. 



Some members, at least, of this group nre prosiphonate, and deserve 

 the designation "ammonite" as much as Lobiies of the Trias, for simplicity 

 of the septa is no longer considered as a distinctive mark of the goniatites. 



Hyatt considered the Gly})hioceratida3 as a family, but E. Haug" is of 

 the opinion that it is rather a group of morphological equivalents than a 

 genetic series. Haug even places Aganides and its descendants in a different 



"Grundziige tier Palfeont., p. .S98. ''Ueber devonische Ainnioneeu, d. 84. 



<■ Etudea sur les Goniatites, p. 39. 



