HISTORICAL SKETCH. XXV 



-subordinate value of the jaw structure (which Semper considered of 

 much less moment them would be thought from the above table), 

 but in the partial recognition of the value of features of the 

 geuitalia, teeth, mantle, foot-grooves, etc., here for the first time made 

 much use of in classification. The great number of genera investig- 

 ated anatomically, and the admirable way in which the work was 

 done, have made Semper's work a classic in malacological literature. 

 The principal defects of the classification are the exaggerated im- 

 portance given to the mucus tail gland, and the structure of the 

 jaw. Moreover, shell characters were practically ignored an ex- 

 treme view, not borne out by broader investigations. 



During the Albers-Martensian epoch, much good detail work 

 upon the anatomy of Helices has been done by investigators using 

 Die Heliceeu and Semper's Reisen as their main reference books. 

 Among these may be mentioned the work of W. G. Binney, Wieg- 

 mann, PfefFer, Schuberth, Brancsik, Lehmann, Fischer, Tapparone- 

 Canefri, Hutton, Hedley, Suter, Hesse, Pollonera, Braun, Morse and 

 others referred to in the text of this volume. Moreover, the advance 

 in knowledge of the shell has been unparalleled, many acute and 

 talented conchologists giving their energies to the elucidation of the 

 Helix faunas of every quarter of the world, and bringing to scientific 

 knowledge a vast number of interesting species, as well as adding 

 enormously to the data for zoogeography. 



During the years 1889-1892 the writer published anatomical data 

 upon various Helices bearing upon a new classification of the entire 

 group, these memoranda being practically the basis of the present 

 volume. 



The Morphologic und Systematik des Genitalapparates von Helix, 

 by Dr. H. von Ihering, appearing in 1892, has exercised a wide in- 

 fluence upon views of Helix classification, and placed the main 

 European genera upon a firm basis. In this powerful essay, v. Iher- 

 .ing adopts the second division of Sempers' Odontognatha as a group 

 of family rank, the Helicidce, with the following genera: Xerophila, 

 Fruticicola, Helix [=Pentatsenia Schm.], Campylcsa, Gonostoma, 

 Dorcasia [=Eulota], Cochlostyla. He also treats of Neohelix 

 (new name for Poiygyra Say), but does not attempt to show its 

 affinities; and the exotic Helices of which the relationships were 

 unknowu to him are placed under the new genus Parahelix. 

 The great merit of this work lies in its advanced views re- 

 garding the value of the various modifications of the genitalia in 



