VU1 INTRODUCTION. 



The principal folds or teeth have definite positions and are 

 homologous throughout the group. The terminology now in 

 use is an amplification of that of Pfeiffer, 1848 (Monographia 

 Heliceorum, ii, p. 300). 



All teeth or laminae upon the parietal and columellar mar- 

 gins are called lamella, whatever their shape; all within the 

 outer lip are called folds or plica. In the following table the 

 names of the secondary, usually variable teeth, are italicized. 



fTwin lamella, parallel lamellae. ") Lamella angu- 



Angular lamella, spiral lamella. laris and I".. 



{uujLcuu wan Parietal lamella. { parietales. Plis 



Infraparietal lamella. J supe'rieurs 



TT ,1 f Supracolumellar lamella. ~] Lamellae 



I Columellar lamella. [ columellares. 



I Subcolumellar lamella. ) Spindelfalten 



f Sutured and Suprapalatal folds. "] 



w:*i, *u Upper palatal fold. | Plicae palatales 



Within the Interpalatal folds. and Plica 



mar^ns Lower palatal fold. basalis. 



Infropalalal folds. Gaumenfalten. 



L Basal fold. J 



A suprapalatal fold, when situated close below the suture, 

 is often called a sutural fold. 



The parietal and columellar lamellae and the lower palatal 

 fold usually are at the angles of an equilateral triangle, when 

 the said fold is not deeply immersed. This is useful in fixing 

 the identity of the plicae, not always clear in multidentate 

 forms, or those in which there has been extensive reduction 

 of teeth. 



Some authors have designated the folds within the outer 

 lip by number, 1, 2, 3, etc., from the upper downwards. This 

 serves very well for descriptive purposes, but the homologies 

 of the folds are entirely lost, since the upper one may be a 

 sutural, a suprapalatal or an upper or lower palatal. This 

 also affects the identity of the folds below the first. The 

 second fold in one species may be homologous with that called 

 first or third in another. 



TOOTH FORMULAS. Several modes of briefly stating tooth 



