1876.] 361 [Hyatt. 



and for that reason the law of priority has been universally recog- 

 nized and mercilessly applied. Waagen, and all other German 

 Paleontologists who have quoted his names, have disregarded this law 

 in a wholesale manner. The only reason for this conduct, and the 

 most charitable one which can be given, is, that they considered the 

 new names proposed by Prof. Agassiz and myself as untenable, and 

 unworthy of their adoption. This reason, although perhaps suffi- 

 cient to themselves and their followers, is no justification for a viola- 

 tion of the rights of priority. The laws of nomenclature do not 

 permit them to describe the same family groups as new genera with 

 new names. New views of the relations of well known species can- 

 not be represented by new generic names because the grouping 

 happens to include a half dozen or more of the previously described 

 genera. What a fearful maze of difficulties this process would lead 

 to if generally adopted! Every man, or set of men, would of course 

 have the same privilege. For example, let us suppose that in my 

 own recent paper on the " Genetic Relations of the Angulatidae," in 

 the Proceed, of the Bost. Soc. Nat. History, Vol. xvn, May, 1874, 

 I had originated a new name for the genus iEgoceras of Waagen, 

 because his generic characteristics are of no value for the distinction 

 of groups of generic significance. The genus iEgoceras, according 

 to Waagen, contains forms as widely separated as Psiloceras plan- 

 orois, belonging to the Arietidse, JEgoceras angulatus, one of the 

 Angulatidse, Androgynoceras Henleyi, one of the Liparoceratidae, and 

 Cceloceras Pettos of the Dactyloidse. According to their development, 

 mode of occurrence in time, and all their adult characteristics, 

 except perhaps " the undivided, horny character of the Aptychus," 

 these forms are perfectly distinct from each other. 



The Psiloceras becomes the parent form of the Arietidae in the 

 Lias, the jEgoceras angulatum of another distinct series differing 

 wholly in development and form in the same formation. Both of 

 these are probably traceable to a common ancestor in the Trias, 

 according to Waagen and Mojsisovics, 1 and therefore it may perhaps 

 be considered that it is legitimate to join them, but what can be said 

 with regard to the remaining forms? Androgynoceras Henleyi is di- 

 rectly traceable to Deroceras Dudressieri, the affinities of which can- 

 not be settled with our present knowledge conclusively; but what 

 evidence there is, however, in the development of the young shows 



iSee also my paper on the " Genetic Relations of the Angulatidae," in these 

 Proceedings, Vol. xvn, p. 15. 



