lymnvEim: of north America. IX 



is a wide field for much valuable work in this direction. In Chapter 

 III the geographical distribution of the family is discussed and a new 

 division of North America into faunal areas is proposed. The tables 

 of comparative distribution will doubtless prove of interest to students 

 of this phase of the subject. The discussion of the post- and pre-glacial 

 distribution is far from being as full or complete as could be wished, 

 but seems to -be the best that can be presented in the light of our pres- 

 ent knowledge of pre-glacial Lymnaeas. 



In Chapter IV an effort has been made to summarize our present 

 knowledge concerning the extinct species of American Lymnseas, and 

 it is believed that the correlation of the fossil species with those of re- 

 cent times will prove of interest. The majority of the fossil species 

 are illustrated by the original figures. The list of fossil Lymnseas is 

 believed to be fairly exhaustive. Chapter V contains an historical 

 sketch of previous monographs. In Chapter VI a new classification 

 is proposed, based on the comparative characters of shell, radula and 

 genitalia. Many malacologists will not agree with the author in thus 

 subdividing this group ; in so doing he has only followed the trend of 

 modern taxonomy. Chapter VII embraces a consideration of the no- 

 menclature. It is believed that the instructions for collecting and pre- 

 paring Lymnseas for dry and anatomical study, in Chapter VIII, will 

 prove helpful to those having little experience in this subject. 



Chapter IX includes the systematic discussion of the Lymnseas of 

 Middle and North America. Each species is discussed under the fol- 

 lowing heads :_ 



Bibliography. 



Description of shells with measurements. 



Location, number, and catalog number of type specimens. 



Type locality. 



Description of Animal. 



Description of Jaw. 



Description of Radula. 



Description of Genitalia. 



Range or Geographical Distribution. 



Records of authentic localities arranged alphabetically by states. 



Geological Range. 



Records of fossil specimens. 



Ecology. 



Remarks. 



