224 



THE CHICAGO ACADEMY OF SCIENCES. 



situated centrally; concave margin with a strong median pro- 

 jection; anterior surface smooth (Fig. 57, J). 



Radula formula: f +f+|+i+f+f+l (21-1-21); central 

 tooth as usual, the central cusp not being as long as in the 

 other species mentioned; laterals eight in number, the outer 

 side cusp being longer than usual; marginals similar to those 

 of retusa, excepting that in the first five the inner cusp is not 

 bifid and there are but two outer side cusps; all of the cusps 

 are very long and bear sharp cutting points (Fig. 57). 



Genitalia: Not examined. 



Distribution: "Canada to Georgia, west to Minnesota, 

 Montana, Utah, Texas and California." (Pilsbry.) 



Geological distribution. : Pleistocene; Loess. 



Fig. 57. 



Radula of SUCCINEA AVARA Say. (Jaw after Binney, radula original.) 

 c, central tooth; 1, 8, lateral teeth; 9, first intermediate marginal; 14 sixth 

 marginal; J, jaw. 



Habitat: Found plentifully under wet boards and logs 

 and at the roots of vegetation situated in moist or wet locali- 

 ties. The vegetation beneath old wooden bridges is always a 

 good locality for this species^ 



Remarks: Avara is distinguished from the previous species 

 by its long spire and nearly round aperture. The movements 

 of this species are always slow and deliberate, and it lacks the 

 energetic motions of its relatives, o valis and retusa. The sutures 

 are sometimes very deep and somewhat channeled. The species 

 is not very common, except in a very few localities, but is found 

 sparingly everywhere. 



