THE NAPLES FAUNA. 



I. GONIATITIN^E. 



Prefatory. 



In the following pages an effort is made to elucidate the actual values of 

 species of given or allied genera in a single fauna, and to express these values 

 in terms of one another. Where fulness and nicety of data have justified, 

 we endeavor to show how a species or variety may be interpreted in the 

 light of a standard or prevalent contemporary type, and to construe the 

 significance of variations in the several structural differentials. 



The meanings of these structural features in the individual have been 

 generally established by the labor of many students of cephalopods, but 

 their application to the portrayal of the mutual relations in coexistent offspring 

 of the same stock has not been so often attempted as to render new illustra- 

 tions of these facts superfluous. These points are lost sight of in none of 

 the forms considered, though they may be involved with descriptive detail. 

 The purpose throughout has been less to seek phylogenic clues than to present 

 ontogenic values. 



GONIATITES (vulgate). 



Family Primordialidae, Hyatt. 

 Genus Maxtkooeras, Hyatt. 



Type of Manticoceras intumescens, Beyrich. 



In various of the papers already cited we have expressed the opinion that 

 the species described by Professor Hall in 1860, as Oroniatites Pattersoni*, is 

 throughout of the same specific type as that described by Beyrich at an earlier 

 date as Groniatites intumescens. There can be no possible controversy on this 

 point, which is confirmed not alone by the general agreement in all normal 

 mature shells, but enforced at every stage of the more minute analysis to 

 which the species is here subjected. It will presently be noticed that this 

 form, which may be regarded as the normal expression of the specific type, is 

 accompanied by other well defined variations of the same type. 



Incidentally, in the comparison of our variations with the diverse forms 

 referred by European authors to Goniatites intumescens, opportunity will be 

 afforded of presenting the fact that, notwithstanding such variations of expres- 

 sion, the specific type is firmly maintained beneath such modifications. Just 



* A bibliography of this and other local expressions of Gon. intumescens occurring in this fauna, is given at the close 

 of the discussion of this species. 



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