112 



ON THE LAND AND FRESH-WATER 



of the beaks : generally much broader from the umbo to the 

 ventral margin, than in the opposite direction : beaks elongated 

 into an obtuse point : anterior portion shortly rounded, but not 

 truncate ; posterior end forming a rounded, slightly pointed angle 

 with the very convex ventral margin. Surface very finely striated. 



<8> 



• O 



o 



Figure 10. 



Pisidium ahditum, Haldeman. 



Shell ovate, orbicular, not very inequilateral ; ventricose ; beaks 

 prominent, rounded : general outline very variable, sometimes very 

 oblique ; in others the umbones almost central, the general form 

 being nearly circular ., but elongated and very bluntly pointed 

 posteriorly : surface striated, the striae stronger than in the prece- 

 ding species. 



LIMNJEHLE. 



Figure 11. 

 Limncea ampla, Mighels. 



"L. testa ampla, subovata; anfractibus quinque, convexis, 

 superne geniculars]; sutura valde impressa ; spira brevi ; apertura 

 lata, ; umbilico profundo (?) ; columella valde plicata." 



I have copied the original diagnosis of this very characteristic 

 species from the proceedings' of the Boston Society of Natural 

 History for June 21st, 1843. 



Dr. Mighel's description agrees with our Lower Canadian 

 specimens in nearly every jespect ; but the Brome Lake specimens 



