118 THE NAUTILUS. 



new genera of Baker will then become sub-genera. The sub- 

 genera of Baker will be reduced to sections with one exception, 

 viz. , that of Simpsonia, now Pseudogalba, be retained as a sub- 

 genus. This form seems to the writer, on account of the char- 

 acter of the radula, to be sufficiently different to cause its re- 

 moval from the sub-genus Galba. We have then the following 

 classification : 



Genus Lymncea Lamarck. 



Subgenus Lymnsea contains the stagnalis group. 



Subgenus Pseudosuccinea contains the columella group. 



Subgenus Radix contains L. auricularia. 



Subgenus Bulimnsea contains L. megasoma. 



Subgenus Acella contains L. haldemani. 



Subgenus Pseudogalba (Simpsonia) contains the humilis and 

 obrussa, umbilicata and parva groups. 



Subgenus Galba contains the section Galba, and the palustris, 

 catascopium and emarginata groups. 



The classification recommended above has certain advantages 

 over that proposed by Baker in that it indicates differences be- 

 tween groups of snails but does not commit one to place a shell 

 the anatom}^ of whose animal is unknown in a given genus. It 

 can be provisionally placed in a subgenus by superficial resem- 

 blance and if later changed will not affect the generic name. 

 It is by the generic name that animals are catalogued. This is a 

 very important practical matter and one that cannot be too 

 much emphasized. To change generic names without an over- 

 whelming amount of evidence in favor of the change is hinder- 

 ing instead of advancing the science. Species and minor groups 

 on the other hand cannot be too much subdivided. It is an 

 advance to describe every variation that can be distinguished. 

 Of this work Bateson (Problems of Genetics, p. 249) says :- 

 "They will serve science best by giving names freely and by 

 describing everything to which their successors may possibly 

 want to refer and generally by subdividing their material into 

 as many species as they can induce any responsible society or 

 journal to publish." It must not be thought that the writer of 

 this is trying in any way to slight the value of Baker's work. 

 It is a work of very great value and splendidly arranged. The 

 clear statement of what we know of the group and what we do 

 not know is most important. It is a model which many 

 should follow. It has been the constant companion and guide 

 of the writer for the past two years. He does not wish this 

 paper to be considered a criticism but rather as an appendix to 



