246 HELJCELLA. 



certain forms a spermatophore of unusual size is found, having the 

 rod-like form and chitinous texture noticed in Leptaxis, but with 

 serrate edge. 



Helicella is allied to Hygromia in the simple-lipped shell, simple 

 form of dart and frequent duplication of the dart sack. It differs 

 from Hygromia in having the right eye-retractor pass to the left of 

 the genital system instead of between its branches, and in the solid, 

 earthy white shell. Outside of these two European groups the 

 double dart sack occurs only in the Mexican genus Lysinoe. The 

 peculiar disposition of the right eye retractor muscle occurs again 

 in Leucochroa. 



The species are very numerous throughout the Mediterranean 

 countries, and many of them show a considerable range of individ- 

 ual variation, and also local or geographic racial forms ; but the 

 number of true species or subspecies is not over one-fourth the 

 number of nominal species, mostly described by authors of the so- 

 called Nouvelle Ecole of France. No individual variation is too 

 slight to be called a " species " by some of these writers ; and a large 

 list could readily be given of " species " founded merely on young 

 shells of well-known forms. Unfortunately for science, many of 

 these worthless names, even some demonstrated to be the young of 

 other species, have been adopted into works supposed to be author- 

 itative, such as Westerlund's " Fauna." The result is that in 

 Europe, where from the number of workers one would expect that 

 the fauna would be well worked up and understood, the study of 

 Helices is in a semichaotic condition so far as species work is con- 

 cerned, and infinitely behind the condition of the science in Amer- 

 ica, the West Indies or Australia. 



The tertiary deposits of Europe have afforded but few members of 

 this genus ; and although recorded from lower Miocene deposits, 

 there are few if any undoubted representatives earlier than Pleisto- 

 cene. This seems to indicate that the group is comparatively new 

 to middle European soil. 



The present group has usually been called X&rophila by recent 

 authors ; but several terms proposed by Risso and Gray precede 

 Held's publication, besides the still earlier Ferussacian name 

 Helicella. Even were we to reject Ferussac's term, the next name 

 in order would be Jacosta Gray, 1821, founded on H. explan- 

 ata. In no case can one use Xerophila as a generic name without 

 throwing the rule of priority to the winds. There are, however, 



