Dentition of Pulmonate Mollusks. 70 



III. — Notes on the Jaw and Lingual Dentition of Pulmonale 



Mollusks. 



BY W. G. BIBTNEY. 



Read March 3rd, 1884. 



I propose in this paper to give, both in text and plates, a 

 synoptical view of the jaws and lingual dentition of all the spe- 

 cies of each genus which I have examined, — the descriptions and 

 figures already published having lost a great deal cf their useful- 

 ness by being scattered through the publications of many years 

 of numerous scientific periodicals. I shall also have an opportu- 

 tunity to judge of the limits of variation, and of the amount of 

 reliance to be placed on the characters of these organs for the 

 purposes of classification, 



In the fifth volume of the "Terrestrial Mollusks and Shells 

 of the United States" (Bulletin Mns. Comp. Zool., IV), I have 

 given an account of the various forms of lingual dentition, mode 

 of extraction, etc., and descriptions of those organs in the genera 

 found in the United States. These I will not repeat here ; but, 

 in order to understand the terms I use, I will state, that appa- 

 rently the normal condition of the lingual membrane is to have 

 three types of teeth : the central, the lateral and the marginal, 

 named from their position on the lingual. Between the laterals 

 and marginals there are generally several transition teeth, as the 

 change is not sudden. The central tooth normally (that is, in 

 the greatest number of species as yet examined) consists of a 

 quadrate base of attachment (a, b, c, cl, of pi. VII, fig. 1), with 

 expanded lower outer angles, and the whole upper surface re- 

 flected. The reflection (e) is tricuspid (one median,/, and two 



