CEPHALOPOD ADAPTATIONS— THE RECORD AND ITS 

 INTERPRETATION 



By EDWARD W. BERRY 



Department of Geology, Johns Hopkins University 



IT SHOULD be recognized at the 

 outset that the present paper is 

 highly speculative in character. 

 Not that the author has much faith 

 in such a method of attacking a problem, 

 but, as will appear in the sequel, because 

 this is the only method of approach in any 

 consideration of the probable structure of 

 the soft parts or habits of life of the 

 extinct representatives of this very impor- 

 tant class of the Mollusca. 



The abundance of fossils of this class in 

 the English midlands, where William 

 Smith first developed the idea of strati- 

 graphic succession, their similar abun- 

 dance in the historic eastern Alps and 

 elsewhere in Europe near centers of sci- 

 entific population, early stimulated specu- 

 lation regarding the characters of the 

 inhabitants of these fossil shells, and so 

 much has been written upon this subject 

 that it is doubtful whether any of the ideas 

 advanced here have not already been pro- 

 posed in one form or another. I have 

 tried to acquaint myself with the litera- 

 ture, but will not attempt citation in most 

 cases, contenting myself with the fore- 

 going disclaimer of originality. 



The Cephalopoda, whose ancient line 

 extends over at least a hundred million 

 years from the oldest known forms of the 

 Cambrian period to the present, and which 

 easily comprises upward of 10,000 known 

 extinct species of great variety of form 

 and presumably of habits, is represented 



in existing seas by a single restricted 

 (Willey, 190Z, recognizes four species) 

 genus with an external shell — the familiar 

 pearly Nautilus; by the less known mono- 

 typic genus Spirula, with an internal shell; 

 by the variety of active squids and cuttles, 

 with an internal highly modified vestige 

 of a shell; and by the less active octopus 

 tribe, without any trace of a shell. 



Throughout the greater part of the 

 geological record their representation in 

 the rocks will naturally be the shelled 

 forms, which alone furnish the requisite 

 hard parts for normal preservation as 

 fossils. Among these the great group of 

 ammonites, with their highly specialized 

 septa, have been entirely extinct since 

 Cretaceous time. (I do not think that I 

 need waste space in refuting Steinmann's 

 idea that the existing dibranchiates are 

 their direct descendants.) The racial 

 history of the ammonite order extended 

 from the late Silurian to the close of the 

 Upper Cretaceous — an inconceivably long 

 period, during which they developed a 

 multitude of forms, and they were easily 

 the dominant cephalopods throughout 

 much of the Mesozoic era. 



Since the existing shell-less forms are 

 geologically modern and show every 

 indication of post-Paleozoic evolution 

 culminating in modern times, they afford 

 but slight basis for comparison with the 

 multitude of shelled forms that go back 

 to the oldest fossiliferous rocks. The 



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