HELICOIDEA. 19 



Paeyphanta, Albers, 1850. 



Bistr. — New Zealand, Australia, P. Biisbyi, Gray (xciii, 82). 



Shell widely umbilicated, depressed, covered by a thick, 

 shiuing, coriaceous epidermis, enveloping the peristome ; aper- 

 ture oblique, semilunar; peristome simple. 



** Gnathophora. Mouth with jaw. Modern malacologists 

 have arranged the families of this division of the Pulmonata in 

 accordance with the structure of the jaw, and to a certain extent 

 this accords with the arrangement by external characters — mainly 

 of the shell. I adopt 



f Holognatha. Jaw simple, without superior appendage. 

 Helices, Bulimi, Cylindrellse, Pupse, Limaces, etc. 



f f Elasmognatha. Jaw with a superior quadrangular accessory 

 plate. Suecinege. 



■]■ Holognatha. 



Includes, as shown above, most of the terrestrial pulmonates. 

 A further division has been attempted according to the orna- 

 mentation of the jaw, but the number of observations made 

 upon this organ are not sufficiently numerous to justify a classi- 

 fication in accordance therewith ; particularly as the groupings 

 heretofore effected' are often in disaccord with obvious relations 

 of the shell. 



The arrangement followed in these pages is mainly that of 

 Pfeiffer's " Nomenclator Heliceorum Viventium," but with some 

 modifications and additions. The naked snails I have preferred 

 to interpose between the Helices and Succinege, as proposed in 

 Gill's Classification (vol. i, 266), rather than preceding the 

 Helices, as in Fischer. 



I give herewith the names and descriptions of the proposed 

 divisions of the Holognatha, founded upon jaw characters, with 

 the principal genera which have been referred to each. Upon 

 the value of these characters, see Binney's remarks (vol, i, 261). 



I, Oxygnatha : Jaw smooth, edge cutting, often with a median 

 prominence, Philomycus, Limax, Tennentia, Parmacella, Heli- 

 carion, Ariophauta, Nanina, Rliysota, Vitrina, H^'^alinia, Zonites, 

 Leucochroa, Rumina, Clausilia ; perhaps also Phania, Planispira, 

 Solaropsis, Otala, Caracolla, Labyrinthus. 



II, Aulacognatha : Jaws finely and regularly grooved, edge 

 crenulated, Ena, Pupa, Discus, Yallonia ; perhaps also Sagda 

 and Hygromia (Fruticola). 



III, Stegognatha : Jaw finel}^ plicated ; the plications imbri- 

 cated, parallel or oblique to the centre. Punctum, Bulimulus. 



lY. Odontognatha : Jaw strongly ribbed, edge toothed. Yeroni- 

 cella, Arion, Ariolimax, Anadenus, Pellicula, Peltella, Moreletia ?, 

 Pfeifferia, Chlorgea, Axina, Pythohelix, Helicobulimus, Cochli- 

 cellus, Jacosta, Euparj'pha, Eulota, Triodopsis, Trigonostoma, 



