Xlviii NOMENCLATURE. 



not included by Ferussac in his group, while lapicida was, we are 

 obliged to consider the latter species the type of Helicogona Fer. 

 Some authors demand that a generic name to be accepted, must be 

 not only appropriate in meaning, but also be correctly limited by its 

 describer; but such a course would only result in utter confusion. 

 Thus, if correct limitation be insisted upon, we might have given 

 new names to about half the genera as recognized herein, for fully 

 that many are composed of materials never before brought into the 

 present associations and groupings. Instead of such a course, we 

 have invariably tried to select for each group, the oldest name ap- 

 plied to any of its members. 



Regarding specific nomenclature, we believe that the dictum, 

 " once a synonym, always a synonym," is the only satisfactory 

 course. Thus, Helix edwardsi Cox was changed to H. nigrilabris 

 because there was a prior Helix edwardsi of Bland ; and this change 

 holds, even though the shells of Cox and of Bland are now known 

 to belong to different genera. On the other hand, Polygyra hemp- 

 hilli W. G. B. is not held to be preoccupied by the earlier Helix 

 hemphilli Newc., because Binney described his species as a Trio- 

 dopsis, not a Helix; and as hemphilli W. G. B. is a Polygyra, and 

 hemphilli, Newc. a Pyramidula, there has never been a duplication 

 of the binomial term " Helix hemphilli" 



THf 



{ UHIVEBSITY 



