150 PROCEEDINGS OF THE ACADEMY OF 
Goutpruss. Verzeichniss der bis jetzt in der Rheinprovinz und 
Westphalen beobachteten Land- und Wasser-Mollusken, nebst 
kurzen Bemerbrengen uber deren Zungen, Krefer, und Liebesfeile. 
From Verhandlungen der natushistorischen Vereins der preussi- 
schen Rheinlande und Westphalens. 13 Jahrgang. Bonn, 1856. 
SEMPER Landmollusken. Reisen in Archipel der Philippinen. 
Wiesbaden, 1873. 
HEYNEMANN. LHinige Miltkeilungen uber Schneckenzungen 
mit besenderer Beachtung der Gattung Limax. From Malako- 
zoologischer Blatter, X. 1862. 
Von Martens Die Heliceen von Jon. Curist. 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 teeth 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 pl. III. fig. 1, 6, 1 have 
selected the part of the membrane where the marginal teeth have 
a very blunt cusp, while in fig. 4, b, 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 by Dr. Leidy, 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 
pl. XVI. 
