CONCHOLOGY. 



shell being liberated, or detached, univalve, with the spire regular 

 and flat; base umbiUcate: the umbilicus sometimes obliterated by 

 age : mouth entire, very open, with acute margin : carina acute. 

 Shell tiled, or covered with extraneous matter agglutinated to its 

 surface. This genus is adverted to by the French writers, but is not 

 adopted by them. Lamarck retains the species among the Trochi, 

 as it stood before in the Linnaean Systema Naturae, but with another 

 change of nomenclature, being denominated by that author Trochus 

 Agglutinans, 



That portion of the group or mass which is placed in the upper 

 part of our plate exhibits the pyramid or spire of the carrier shell 

 which is encumbered with the adhesions. It is much depressed, 

 flattened and deformed by these extraneous fragments. The single 

 denotes this shell. 



In the group disposed in the lower part of the plate the single * 

 denotes the principal carrier shell. It is the base of the shell that 

 becomes obvious in this mass, and which, as before described, is free 

 from any adhesions, these being situated upon the pyramidal sides 

 and margin of the shell, but none adhering to the base. 



There is one figure in the lower group distinguished by two J 

 in which the true form of the shell is shewn as it appears when 

 the adhesions have not impeded the growth and elevation of the 

 spire. 



The shell marked with three is of smaller growth, more 

 depressed and angulated from some accidental cause. 



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