150 PROCEEDINGS OF THE ACADEMY OP 



Goldfuss. Verzeiebniss der bis jetzt in der Rheinprovinz und 

 Westpbalen beobachteten Land- und Wasser-Mollusken, nebst 

 kurzen Beraerbrengen iiber deren Zungen, Krefer, und Liebesfeile. 

 From Verhandlungen der natushistorisehen Vereins der preussi- 

 schen Rheinlande und Westpbalens. 13 Jabrgang. Bonn, 1856. 



Semper Landrnollusken. Reisen in Arcbipel der Philippines 

 Wiesbaden, 1873. 



Heynemann. Einige Miltkeilungen liber Schneckenzungen 

 mit besenderer Beacbtung der Gattung Limax. From Malako- 

 zoologischer Blatter, X. 1862. 



Yon Martens Die Heliceen von Joh. Christ. Albers. Zweite 

 Ausgabe. Leipzig, 1860. 



These are the principal works referred to. The references to 

 shorter papers in various periodicals will easily be understood. 



On my Illustrations. 



I have endeavored to give a good view of the central, lateral, 

 and marginal teetli of each species, with the transition teeth of 

 many of the species. The portion of the membrane chosen is> 

 different in the various species of each genus or subgenus, in order 

 that the variations in the form and development of cusps, and 

 cutting points may be shown. Thus on pi. III. fig. 1, 6, I have 

 selected the part of the membrane where the marginal teeth have 

 a very blunt cusp, while in fig. 4, 6, they are shown much more 

 graceful. It must constantly be borne in mind that on any one 

 membrane the teeth vary considerably in regard to this point. 



In illustrating the general arrangement of the teeth upon the 

 lingual membrane in each genus or subgenus, I have used the wood- 

 cuts in the text prepared for my former works and papers, mostly 

 by Mr. Morse, and a few b} 7 Dr. Leicly, prepared for my father's 

 work. It must be remembered that these figures do not represent 

 correctly the characters of the individual teeth. 



I have also used in the text figures of the jaws of many genera 

 and subgenera, prepared for the Land and Fresh Water Shells of 

 North America, Part I. The jaws of the more recently described 

 genera and subgenera I have myself drawn by camera lucida in 

 pi. XVI. 



