Miss Agnes Crane — Recent and Fossil Cephalopoda. 497 



progressive development in the history of the class, so far as relates 

 to the first appearance of the lowest forms in the primeval oceans, 

 and to the succession of that more highly developed group, which 

 mainly represents the order at the present day, cannot reasonably 

 be denied. The occurrence of certain comprehensive types, uniting 

 characters which subsequently became distinctive peculiarities of 

 diverse genera, must also be admitted. Thus, as Professor Owen ' 

 has shown, in the Belemnitidce are united the internal chambered 

 and siphnnculated structure retained solely in the existing Spirula, 

 while the horny armature of the tentacles is at present restricted to 

 one genus of the living Calamaries, but he does not fail to point 

 out that the perfect preservation of the fossil forms has revealed the 

 fact that the armature of the Secondary Cephalopods was as highly 

 organised as that of any of the species inhabiting our present seas, 

 and is not, therefore, indicative of any great rate of progression, not- 

 withstanding the enormous intervals of time that must have elapsed 

 between the Secondary and the Recent period. Again, according to 

 Sir Charles Lyell,^ "The rate of progression has been slow indeed, if 

 the only step realized between the Lower Silurian and modern times 

 can be expressed by the passage from the tetrabranchiate to the di- 

 branchiate Cephalopod, a rate of progress that might require a course 

 of ages anterior to the Silurian epoch, as great as that which has since 

 elapsed in order to bring about a gradual evolution from a Bryozoon 

 to an Orthoceras." The important testimony of M. Joachim Bar- 

 rande,^ founded on a special and extended survey of more than 2,500 

 Palaeozoic species, is also directly opposed to the theory that one form 

 has been evolved from another. That illustrious palaeontologist, who, 

 from his vast labours among the Palaeozoic rocks of Central Germany, 

 may be fitly entitled the " Murchison of Bohemia," contends that 

 the recent Nautilus possesses the same essential characters as the 

 earliest known forms so universally distributed at the base of the 

 Lower Silurian formation,* that a detailed examination of the struc- 

 ture of the Tetrabranchiate Cephalopods, whether as applied to the 

 position and diameter of the syphon, the size, composition and 

 ornamentative characters of the shell, furnishes no evidence in 

 support of the theories of descent by modification, natural selection, 

 or the survival of the fittest ; and further, that the stability of 

 generic types, and the distribution of the group in geological time, 

 is equally opposed to them. The complex forms, moreover, often 

 precede the simpler ones, while those which appear to be inter- 

 mediate follow the genera which thej'- might otherwise be supposed 

 to connect. It must, however, be noted that the arguments as to 

 the relative simplicity, or complexity, of structure, are founded 



1 Phil. Trans., 1844. 



2 Principles of Geology, vol. i. p. 150, ed. 1872. 

 ^ Etudes Ge'nerales, etc., Barraude. 



* It must always be borne in mind, when arguing from these early fossil molluscan 

 remains, that we have only the shells preserved to us. "We know nothing of the 

 animals. Our argument then is founded on assumption, and must be treated ac- 

 cordingly. See " Distribution of the Cephalopoda in Silurian Countries," by 

 J. Barrande. Eeviewed in Geol. Mag. 1870, Vol. VII. p. 490. 



DECADE II. VOL. T. — NO. XI. 32 



