286 HELICODONTA. 



ing mainly in the reflexed, lipped peristome, and more or less degen- 

 erate dart apparatus. Helicodonta is not in the least allied to the 

 American or Indian toothed Helices, or to the so-called Gonostoma 

 of California. 



The circum-Mediterranean region is the headquarters of this 

 genus, although a few forms occupy central Europe, and one, obvo- 

 luta, has obtained a foothold in southern England. In south-east 

 Asia it reappears in a number of specific forms comparable to the 

 European species obvoluta and diodonta, but not readily falling into 

 the sectional groups established for European forms. The Canary 

 Islands are nearly the westward outpost of the genus, one species 

 only occurring in Madeira. 



The name Helicodonta was originally proposed for all toothed 

 Helices ; but was restricted by Risso, in 1826, to H. obvoluta. As 

 no other name for the group appeared before 1833, there is no ques- 

 tion as to the propriety of reverting to this one, especially since the 

 names in common use, Gonostoma and Trigonostoma are preoccu- 

 pied, and must, in any case, be rejected. Besides two species still 

 retained in this group, Ferussac included in Helicodonta members 

 of the prior genera Polygyra, Pleurodonte, Cepolis, and Anostoma, 

 as well as of the later groups Strobila, Gorilla and Petasia. The 

 term Anchistoma of the Adam's brothers (1855) has been used for 

 Helicodonta by Kobelt and others. It has been attributed to Klein 

 (1753), but his "Angystoma" contains none of the European toothed 

 Helices and, in any case, the genera and species of the Tentamen 

 melhodi Ostracologicce are not of Linnsean form, and antedate the 

 Linmean era. Ehrenberg's contribution to the taxonomy of this 

 group is of little value. He divides the land snails into two series, 

 based on the absence or presence of aperture-teeth : Chilogymnus 

 containing Helix, Caracolla, Bulimus, Pupa, and Chilodon contain- 

 ing Helicodon, Caracollina, Bulimina, Pupina. The genera of 

 Chilodon are all new, although he does not so state ; but, as they are 

 nude names, without a word of diagnosis except what may be 

 tacitly gathered from the above arrangement, and as no species of 

 any of them are mentioned, their bearing on nomenclature is nil, 

 and none of them can be dated from 1831, or adopted at all except 

 when defined by later authors. The group Vortex of Oken (1815) 

 contained depressed Helices and Zonitids of many groups, and, as it 

 is a composite group, and the name was not used in especial connec- 

 tion with Helicodonta until after the publications of Ferussac and 



