THE NATURAL HISTORY SURVEY. 43 
the radular belt; the rest of the tooth is reflected (2) and pro- 
vided with three cusps, a median (4) and two lateral (3), and 
each cusp has a cutting point (5,6). The lateral and marginal 
teeth may be divided in the same manner into cusps and cutting 
points (b,c). The lingual teeth of all pulmonate mollusks are 
divisible into two types (1), the quadrate (a) and (2) the acule- 
ate (c). The latter has no reflected portion, but a single thorn- 
shaped cutting point arises from its sole-shaped base of attach- 
taent (Fig. 9, c, i, 6).7 
*Those who desire a detailed account of the anatomy of the Mollusca may consult the 
following works: 
Bronn and Keferstein: Klassen und Ordnungen der Weichthiere. 
Tryon: Structural and Systematic Conchology. 
Lankester: ZoGlogical Articles. 
Fischer: Manual de Conchyliologie. 
