EXPLANATION OF THE PARTS OF SHELLS. 27 



Plate III fig. 1, 3, and 14, C C C. Some apertures have 

 a canal at their base, as in Plate XII. fig. 5, 6, 7, and 

 others are devoid of it, as in Plate XIII. fig. 1, 2, 3. In 

 various genera it extends the whole length of the shell, 

 as in the Cypraea, and some of the Cones with depressed 

 spires. It is either entirely open, or it is closed by an 

 operculum or lid, which is usually affixed to the foot of the 

 animal. 



Canal, or gutter, is the inside of the elongation of the 

 aperture, or both lips of the shell of those species with a 

 beak, in which it forms a concave channel or gutter, run- 

 ning from its commencement in the aperture, to the extrem 

 ity or base, Plate II. fig. 10 and 11, Q Q; Plate III. fig. 8, Q. 

 Some species are furnished with two canals, one situated 

 at the junction of the outer lip and body, as in the Murex 

 T ampas, &c. 



Beak, or rostrum, is that lengthened process in which the 

 canal is situate; it commt-nces a little higher up, on the 

 outside, than the insertion of the canal in the inside, which 

 is always distinctly marked by the line of the aperture. 

 Plate II fig. 11, p. This process is not so conspicuous in 

 some of the species of Voluta, but is more marked in the 

 genera Murex, Fusus, Pyrula, &c. 



Pillar, or columella, is that part which runs through the 

 centre of the shell in the inside, from the base to the apex 

 in most univalve shells, and appears to be the support of 

 the spire ; or it may be defined the axis of the shell, round 

 which the whorls are continued from the apex to the base. 

 It is in general grooved or folded ; but, as it is situated in 

 the interior of the shell, a minute description is unnecessary. 

 Plate II. fig. 10 and 12, MM MMM; and Plate III. 

 fig. 9, MMM. The internal edge of its base is frequently 



' described as having plaits, &c. 



: Plaited Columella, having upon it those folds, or plaits, 



' which are the distinguishing characteristic of the Volutae 



i and other genera. Plate II. fig. 7, z. 



I Pit'ar Lip is a continuation of the glossy process with 



which the aperture is lined, and expanded on the columella. 

 c2 



