28 



MANUAL OF THE MOLLUSCA. 



sometimes form a single series, overlapping each other, or there 

 are lateral teeth on each side of a median series. The teeth on 

 the pleursB are termed uncini ; they are extremely numerous in 

 the plant-eating gasteropods. (Tig. 15. A.)* 



Pig. 15. Lingual Teeth of Molhisca. ^ 

 Sometimes the tongue forms a short semi-circular ridge, ' 

 contained between the jaws ; at others, it is extremely elongated, j 

 and when withchawn, its folds extend backwards to the stomach. ! 

 The lingual ribbon of the limpet is longer than the whole ani- 

 mal; the tongue of the whelk has 100 rows of teeth ; and , 

 the great slug has 160 rows, with 180 teeth in each row. \ 



Fig. 16. Tongue of the Whelk. ^ 

 The front of the tongue is frequently curved, or bent quite 

 over ; it is the part of the instrument in use, and its teeth are 



* Fig. 15. A. Lingual teeth of trochns dnerarius (after Love'n). Only 

 the median tooth, and the (5) lateral teeth, and (90) ^ln(n7li of one side of a ._ 

 single row ai-e represented. B. One row of the lingual teeth of cyproea ' 

 europcea ; consisting of a median tooth, and three uncini on each side of it. 



t Fig. 16. Lingual ribbon of buccinum undatum (original), from a pre- 

 pai-ation communicated by ^^n^. Thomson, Esq., of King's CoUege. 



