498 Miss Agnes Crane — Recent and Fossil Cephalopoda. 



solely on an investigation of the characters of the external shell, 

 a test that is by no means a sure indication of corresponding differ- 

 ences in grades of organization of the animals inhabiting them, and 

 therefore the classification of zoologists is rightly based on those 

 internal characters which affect the life-conditions and habits of the 

 animal, — characters of which we are necessarily often entirely 

 ignorant in the case of fossils derived from the Palgeozoic rocks. 

 Again, with regard to the distribution in time, we are confronted 

 with the fact that of the whole 25 Palseozoic genera, no less than 12 

 varied types, or nearly one-half of the whole, occur simultaneously 

 in all parts of the world at the same geological epoch. This wide 

 distribution of the so-termed primitive types is, however, capable of 

 being interpreted by Evolutionists as proof of their antiquity ; and 

 they will probably define the conclusion that they are the first repre- 

 sentatives of the group, as an unsound one, based, as it undoubtedly 

 is, on purely negative evidence, and reply that their predecessors 

 have yet to be discovered in some of the unexplored Cambrian areas. 

 But M. Barrande's most valid objection to the theory of the evolu- 

 tion of the class, one with which I am not competent to deal, is 

 assuredly that founded on a critical investigation of the embryonic 

 characters of the AmmonitidcB and Goniatidce, as compared with that 

 of the Nautilidce. These researches lead him to the conviction that 

 important embryological distinctions exist between the development 

 of the Ammonites and Goniatites, and that of the Naiitilidce, which 

 preclude the reception of the idea that the Secondary Ammonitidoe 

 were derived from the Goniatites, and they, in their turn, from the 

 primitive Nautili. To quote from the able and most instructive 

 anniversary address of the late President of the Geological Society,^ 

 Professor Martin Duncan, F.E.S., " The examination of the earliest 

 formed portion of the shell of Nautilus and Goniatites indicates 

 embryological distinctions, and, therefore, it is necessary to seek in 

 the remoter Palgeozoic Nautilidce for the ancestors of Nautilus and 

 Goniatites." 



One further point deserves notice, namely, the occurrence at 

 various geological horizons of distinct generic forms, which repre- 

 sented by a few, or possibly by several species, nevertheless die out 

 at the close of that short geological period, and never re-appear. 

 " So careful of the type ?" but no, 



From scarped cliff and quarried stone 



She cries, " A thousand types are gone, 



I care for nothing, all shall go." 



Tennyson's In Memoriam. 



This fact, which is observable in many other groups of organisms, 

 notably in that of the Brachiopoda, as was so clearly explained by 

 Mr. Davidson ^ in his admirable memoir, is explicable only, either by 

 the hypothesis of descent with modification, or by that of the 

 doctrine of special creation. In this instance it would perhaps 



^ Quarterly Journal Geological Society, London, May 1st, 1878, p. 69. 



2 "What is a Brachiopod ? Brighton and Sussex Natural History Society. Feb. 

 11th, 1875 ; Geological Magazine, April, May, June, 1878 ; Annales de la Societe 

 Malacologique de Belgique, 1876. 



