Clarke — The Naples Fauna. 



135 



THE RELATION OF THE GONIATTTLNE ELEMENT OF THE 

 NAPLES FAUNA TO THE SEDIMENTS IN WHICH IT IS 

 INVOLVED. 



From the habitude of living cephalopoda it has been inferred by recent 

 writers, of whom we may specially cite J. Tv altiier,* that the ammonites, and 

 Ave may properly conclude, the goniatites likewise, were animals which crept 

 about over the sea bottom by the agency of their tentacles. "Nautilus, 11 

 says Waltiier, "does not, as commonly assumed, swim as nekton in open sea 

 nor does the animal travel about as plankton at the surface. On the contrary 

 Nautilus is a benthonic animal, which crawls about on the sea-bottom ; 11 * * 

 only " the empty Nautilus shell floats on the surface. The animal of 

 Spibula has a sessile benthonic habit, and its empty shell is, also, so con- 

 structed that it floats on the water surface. * * * The same is true of 

 Sepia." Granting that this habit of life was likewise that of the extinct 

 cephalopoda (and with present knowledge there is no justification for a con- 

 trary assumption), Ave must concede the great force of Walther's arguments 

 in so far as they go to indicate the A*ery great caution required in interpreting 

 the meaning of occurrence among the ammonoids. If the vast majority of 

 these superabundant fossils are, in pursuance of this argument, transported 

 shells floated, as one may aay, out of their facies, and dropped in sediments 

 Avhereon they had not lived and among organic species with which their rela- 

 tions are wholly posthumous, the palaeontologist, in determining when these 

 ammonoids are within their oavu proper fauna, has before himself a host of 

 problems of the utmost delicacy. 



AVe believe that the influence of this doctrine may easily be carried 

 too far. Abundant cases may l>e cited in which no doubt can arise as to 

 appertinence of ammonoids to the sediments in which they are contained and 

 the fauna with which they are associated, and lest this fact be overlooked in 

 the application of Walther's arguments, that author has himself emphasized 

 it and cited instances of long continued existence and propagation of ammo- 

 nites upon the very sediments in which they are involved. 



The ammonoids of tne Naples beds bear sufficient demonstration in 

 themselves that they have lived and died in these sediments. And this is 

 doubtless true notwithstanding the fact that the sediments are larirelv aren- 

 aceous and were deposited in comparatively shallow water, and the equally 



* Einleitunc iu cli i Geologic als Uistoriscbe Wissenscliat't ; ud<1 Ueber die LebensweUe fossiler Meo-csthiere (Zeitscli. 

 • I.d. geolog. Gesellscb. vol. 49, Halt 2, 1K97). 



