On certain features of the lateral canals and cranial bones of Polyodon folium. 677 



the so-called dermal bones of the skull of fishes, and that this com- 

 ponent may be found wholly separate and distinct from another, so- 

 called membranous component that may form part of the same bones. 

 Is then this lateral component retained after the sensory organ or 

 organs in relation to which it is developed have disappeared? That 

 it may be retained without a related enclosed organ is certainly 

 shown by the presence, in Cmiger (5), of a postauditory squamosal 

 canal ossicle without such a related organ. 



Palais Carnolès, Menton, 

 May 5th, 1902. 



Literature. 



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3) — , The premaxillary and maxillary bones, and the maxillary and 



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 Nos. 11 and 12, Oct. 1900. 



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Trans. Roy. Soc. London, Part 2, 1878. 



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formation Böhmens, V. 1, Prag 1879 — 80. 



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 1865. 



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 Dissertation, State Hospitals Press, Utica, N. Y., 1899, 



