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 CHAP. XXIX. 



UNIVALVE S: 

 MUREX; Rock y or Trumpet Shell. 



Q. WHAT are the characteristics of the Mu- 

 rex? 



A. A spiral rough shell, often formed with 

 longitudinal membranaceous sutures, aperture 

 terminating in a canal, either strait or turned up 

 backwards, and not inclining either to the right or 

 left. 



Q. Is not the peculiar form of the aperture a 

 distinctive feature ? 



A. Yes, it is generally an oblong, or a perfect 

 oval, and does not gradually contract into a 

 canal, but abruptly opens into it, at the same, 

 or nearly the same width which it retains through- 

 out the whole length of the beak. The straitness 

 of the rostrum is a much more questionable mark 

 than the outline of the aperture, which, when 

 once understood, cannot easily be mistaken. 



Q. From what is the designation of this genus 

 derived ? 



A. From a certain number of its shell, which 

 are rough and rock-like* 



Q. I believe the Tyrian purple, the costly 



