116 



INTRODUCTION TO ZOOLOGY 



CHAP. 



Shell f to 1 inch in diameter, rounded on both sides. Whorls 

 5 or 6. Dark reddish brown in colour, very common in some 

 localities, and always to be had readily from any dealer in 

 aquatic specimens. Eggs 20 to 45 in a flat, oval capsule 

 attached to a leaf. Rasp with 67 teeth in each row, and 

 200 rows. 



Planorbis complanatus ( = umbilicatus). Shell f inch dia- 

 meter ; 5 or 6 whorls. One side of the shell is flat or 



FIG. 66. The Common Trumpet Snail (Planorbis corneus). 



A, Climbing a piece of Canadian water-weed. B, Breathing at the surface ; r, respira- 

 tory aperture. C, Seen from the left side, showing the projecting respiratory lobe 

 of the mantle. 



concave, and hence there is a distinct keel, quite on one side 

 of the middle line of the outer whorl. Mouth of shell 

 rhomboidal. 



Planorlis vortex (the Whirlpool Trumpet Snail). Shell f inch 

 in diameter. Whorls 6 to 8. One side of the shell is convex, 

 and one flat, and consequently here also there is a keel on one 

 side of the body whorl. This species, which is fairly common, 

 can endure drought, lying in a torpid state with the mouth of 

 the shell closed by an " epiphragm." 1 



1 For explanation of this term see p. 127. 



