RAMS-HORN APPLE-SNAIL. Ampulldria cornu-arietis. 

 WATER-SNAIL. Limncea stagnalis. POUCH-SHELL. Physa hypndmm. 



COMMON PLANORBIS. -TlanorMs cdrnein 

 STAIRCASE APPLE-SHELL. Ampulldria scalaris. RIVER LIMPET. Ancylus lacustris. 



and stout footstalks, and the enormously long tentacles are placed just in front of the 

 eyes. At the first glance the creature appears to have four tentacles, but ; on a closer 

 examination, the front pair are seen to be merely developments of the muzzle. In one 

 respect, the Ampullaria seems to be a connecting link between the gill-bearing and lung- 

 bearing molluscs, being said by high authorities to possess a pulmonic or lung sac, in 

 addition to its gills. 



ON the left hand of the illustration the common POND-SNAIL, or LIMNCEA, is shown in 

 the act of climbing up the stem of a water-plant. In all the members of this family the 

 shell is thin, and sufficiently capacious to contain the entire animal when it desires to 

 withdraw itself into its home. The aperture is simply rounded, without notches or 

 ridges, and the lip is sharp. 



The Pond-snail may be found in almost any fresh water, and, if carefully watched, 

 proves to be quite an interesting creature. It can creep with tolerable rapidity after the 

 usual manner of snails, and has besides a curious method of progression without making 

 any exertion of its own. In streams, when the animal has a mind to change its locality 

 without needing to exert itself, it achieves the task of converting the journey into a 

 voyage, and its foot into a boat. This transformation is soon effected, the animal first 

 crawling up some plant that projects out of the water, reversing its position, so that the 

 shell lies undermost, and then hollowing the foot so as to form it into a shallow boat-like 



