INTRODUCTION. x 



arrangements have been proposed. The simplest gives merely 

 the number of teeth on each margin ; thus 2-1-3 denotes two 

 teeth on the parietal wall, one on the columellar and three in 

 the outer and basal margins. If more definite information is 

 to be conveyed, the initials of the teeth may be used, those 

 representing concrescent or united teeth being enclosed in 

 parentheses, as follows: 



a. Angular lamella. s. Suprapalatal fold. 



p. Parietal lamella. w. Upper palatal fold. 



ip. Infraparietal lamella. i. Interpalatal fold, 



c. Columellar lamella. I. Lower palatal fold. 



sc. Subcolumellar lamella. &. Basal fold. 



Thus, (a.p.)-c-u.l.b. denotes the presence of united an- 

 gular and parietal lamellae, a columellar lamella, upper and 

 lower palatal and basal plicae. While more cumbersome than 

 the numerical formula, this has the advantage of showing 

 what teeth are present, information more important than the 

 mere number. The practical utility of such formulas is open 

 to question. Space is saved, but at the expense of those who 

 use the work. 



