84 POLYGYRATIA-PLEURODONTE. 



Helix multispirata Hombr. & Jacq. (Manual, iii, 127) and H. 

 microphis Crosse, have been referred to Polygyratia by authors. The 

 first is probably a Charopa. The other has been made the type of 

 a group Microphyura by Ancey (Bull. Soc. Mai. Fr. v, 375). It 

 belongs to the genus Diplomphalus in Rhytididre (Manual i, p. 114). 



Species. 



P. nuicgregori Cox, iii, 127. New Ireland. 



P. raffrayi Tap.-Can., iii, 128. Western New Guinea. 



*T" *T* *P 



The series of genera next to be considered comprises a majority 

 of the large, solid-shelled Helices of the tropics and southern hemi- 

 sphere, both in the Old World and America. All discussion of this 

 and other primary divisions of the Helices is reserved for tie intro- 

 ductory portion of this volume, but certain brief notes may be of 

 use in this place. These genera share certain peculiarities of the 

 generative system : the female branch is without dart sack or other acces- 

 sor;/ organs ; the male side has the penis continued beyond its papilla- 

 bearing apex in a narrow tube called the "epiphallus," which terminates 

 in a flagellum and vas deferens. In most forms the epiphallus is as 

 long or longer than the penis itself ; but in some (such as Thelido- 

 mus) it is so shortened as to be inconspicuous, or even absent. In 

 Cristigibba this process of shortening has resulted in the com- 

 plete degeneration of both epiphallus and flagellum. In these and 

 similar cases we must not mistake the structure resulting from de- 

 generation for a primitive condition. Such an error would be like 

 holding Ancylus to be a primitive gastropod on account of its (at 

 present) non-spiral shell, or like grouping the limbless lizards, An- 

 guis or Amphisbcena with the snakes. 



In the American forms the penis retractor is inserted upon the 

 penis; in the Asiatic and Australian it is usually upon the epiphal- 

 lus. 



The jaw is generally stoutly ribbed, but often by degeneration of 

 the ribs, smooth ; and this modification is certainly in some cases 

 not a generic or even subgeueric character. 



Genus PLEURODONTE Fischer de Waldheim, 1808. 



=Pleurodonte -f- Lucerna-{- Dentellaria-}- Caracolus -\-Isomeria-\- 

 Labyrinthus -f- Pohjdontes -f- Thelidomus -\- Liochila -f Eurycratera, 

 etc., of authors. 



