Conchology. 69 



and some other univalves which have no regular spire. The 

 base of a shell is denoted in plate iii. fig. 1, by a. 



Apex, the summit of the shell, b. 



Front, the face of the shell, with the aperture placed di- 

 rectly in front of the observer, c. 



Back, that part of the shell which is immediately opposite 

 to the preceding. 



Sides, those parts seen longitudinally in profile, to the 

 right and left when the shell is viewed either in a front or 

 back position, d. 



Body of the shell, (corpus) the first whorl of the spire at 

 the base, fig. 2, e. 



Whorl, denotes one of the wreaths, turns or volutions of 

 the shell, fig. 3, /. 



Spire, comprehends in a general sense, all the whorls of 

 the shell, the first or body wreath excepted, fig. 1, g. 



Crown of the spire, fig. 4, c. 



Suture of the spire or whorls, is the spiral line which sepa- 

 rates the whorls, and which is sometimes sulcated, crenulated 

 or somewhat projecting, fig. 1, h. 



Pillar or columella, is the inner part of the left lip or col- 

 umn, which runs through the shell, from the lower extremity 

 to the tip of the spire, and from which all the spires take 

 their origin; the columella being situated as nearly as possible 

 in the axis of the shell, and serving as its basis and support 

 throughout. It is generally either flat, grooved, folded or 

 truncated in that part which is visible at the opening, fig. 4,i. 



Aperture, called in familiar language, the mouth of the 

 shell, is the entrance to the chamber in which the animal re- 

 sides, and is applicable to the openings of univalve and mul- 

 tivalve shells. The aperture is either entirely open, or closed 

 by the operculum attached to the body of the animal, when 

 the animal retires into its dwelling. This aperture varies in 

 form in different shells, being angular, rounded, semi-lunar, 

 linear or otherwise, and sometimes appear double, the inner 

 margin being surrounded by an exterior one, fig. 2, m. 



Lip, the expansion of the exterior part of the aperture con- 

 stitutes the lip in labiated shells, and the wing in the alated 

 kinds, fig. 4, I. 



Beak or rostrum, is that part at the base which extends in 

 a strait or slightly oblique direction from the bottom of the 

 aperture, and is larger or smaller in different families, fig. 3, n. 



Cojial or gutter, an elongation of the aperture of the shell 

 descending in a groove or gutter-like process. Some kinds of 

 rostrated shells have the canal remarkably conspicuous, form- 



