THE NATURAL HISTORY SURVEY. 219 



at the anterior part of the mantle and extending downward 

 and forward to a point behind the tentacles; sometimes the 

 central stripe, which extends from the mouth over the head 

 to the mantle, is quite large and composed of small black 

 blotches. Length of foot 13.00, width 6.00 mill. Heart situ- 

 ated midway between the anterior and posterior borders of 

 the aperture, to the left of the columella, pulsations regular, 

 sixty-nine per minute. 



yaw: With the usual quadrate, superior appendage com- 

 mon to the genus; cutting portion arched, with a median pro- 

 jection to cutting edge; anterior surface with from three to 

 seven ribs which denticulate both margins (Fig. 55, J). 



Radula formula: ^ + ^>++^> + iy (42-1 -42); central 

 tooth with a subquadrate base of attachment, the lower outer 



Fig. 55. 



Radula of SUCCINEA OVALIS Say. (Original.) c, central tooth; 1, first 

 lateral; 17, 35 marginal teeth; J, jaw. 



corners expanded and the base concave; reflection tricuspid, 

 the central cusp long and wide, nearly or quite-reaching the 

 lower margin of the base of attachment, the side cusps very 

 short; lateral teeth similar to central, longer than wide, bicus- 

 pid, the inner cusp very long and wide, reaching below the 

 lower margin of the base of attachment, the outer cusp very 

 small; the third outer cusp on the first few laterals is rudimen- 

 tary; marginal teethmodifiedlaterals, wider than long, tricuspid, 

 the inner cusp long and wide, acute, and the two outer cusps 

 short, narrow and pointed. All of the cusps are provided with 

 well marked cutting points (Fig. 55). 



Genitalia: See generic description. 



Distribution: Eastern and Central parts of Northern United 

 States, west to Manitoba, south to Arkansas and Georgia; 

 Canada. 



