EXPLANATION OF TERMS. XX1U 



Irregular. With the spires reversed, or turning from left to 

 right when the shell is placed with its mouth downwards. 



Juncture, Junction. The circular line, where one volution 

 or turn of a spire meets another. 



Lamina?. Small thin layers, or plate-like teeth. 



Lanceolate. Shaped like the head of a spear. 



Lateral. Placed on one or both sides. 



Length. Extending from the hinge to the opposite margin ; 

 as in some of the Solenes the length is not one-third of the 

 breadth. 



Linear. Extremely narrow in proportion to its breadth, and 

 of nearly equal diameter throughout. 



Lip. A projection or extension : the margin of the mouth 

 of a spiral shell. 



Lobe. A rounded division. 



Longitudinal. Extending from the hinge towards the front 

 margin, or from the tip to the base. 



Memlranaceous. Extremely thin, like a membrane. 



Multivalve. Having more than two valves. 



Nacred. Highly polished and lustrous, like mother of pearl. 



Ob In construction means reversed : as obconic is the re*, 

 semblance of a cone reversed ; oboval a reversed oval. 



Opake. Not in the smallest degree transparent. 



Orbicular. Quite round or circular. 



Pillar. The support which passes through the centre of a 

 spiral shell, and round which the volutions turn. 



Posterior. The hinder slope or margin of a bivalve shjell, is 

 the side opposite to that where the cartilage is placed. 



Radiate. Furnished with rays, proceeding either from the 

 centre, or the hin ^e to the margin. 



Reflected. Turned backwards. 



Regular. With the volutions turning from the right to the 

 left when the shell is placed with its mouth downwards. 



Reversed. Applied to a spiral shell whose volutions turn in 

 a contrary direction to the generality of shells ; that is, whose 

 volutions turn from the left hand to the right. Hold up a 

 spiral shell with the tip or smaller end upwards, and the aper- 

 ture towards you : if the mouth or aperture be placed on the 

 right hand of the pillar, and the volutions wind round in that 

 direction, it is called a regular spire; but if the mouth be 

 placed on the left hand of the pillar, and the volutions follow 

 that direction, it is a reversed or irregular shell. 



Re'ic .lite. Ribbed or marked both lengthways and across, 

 so as to form a kind of network. 



Rctuse, 



