A MANUAL OF AMERICAN LAND SHELLS. 55 



forming a double jaw, and to be compared to the accessory plate of 

 the jaw o£ Succinea; lingual membrane of SeZia?; central tooth of same 

 form and usually of same size as the laterals, tricuspid ; marginal teeth 

 quadrate, wide, low, denticulated. Shell generally multispiral, elon- 

 gated, conic, or cylindrical; aperture small, often narrowed by internal 

 teeth or lamellae. 



Pupa. 



Vertigo. 



^tropMot 



Holospira, 



Family STENOGYRID^. 



Jaw ribbed or finely wrinkled, thin, arched; lingual membrane with 

 extremely small central tooth; lateral teeth tricuspid; central cusp long 

 and narrow ; side cusps of subequal length ; marginal teeth quadrate, 

 very low, wide, tricuspid or multifid. Shell generally elongated, poly- 

 gyral, shining, translucent or calcareous, striate; apex more or less 

 obtuse; peristome simple, rarely reflected ; columella often truncated 

 Of plicated. 



Sfenogyra s. g. Bumina, OpeaSy Melaniella. 



Ferussacia. 



CceciUanella. , 



Family ORTHALICID^. 



Jaw thick, solid, composed of a median triangular piece, with base 

 corresponding to upper margin of jaw, and near the apex of which con- 

 verge on either side oblique imbricated plates, free below, adherent 

 above. Lingual membrane with oblique rows of teeth. Central and 

 lateral teeth with quadrangular base, with central cusp more or less 

 obtuse, generally very much expanded, with rudimentary side cusps ; 

 marginal teeth quadrate, of same type. External, Bulimus-like shell. 



Orthalicus. 



Liguus. 



Elasmognatha. 



Family SUCCINID^. 



Tentacles but little developed or wanting. Jaw surmounted by an 

 accessory quadrangular plate. Central tooth of the lingual mem- 

 brane tricuspid, of the same size as the laterals, which are tricuspid 



