
MOLLUSCS, VERMES AND HYDROZOA 

deep and the ap- 
ertureoval. The 
body is yellqwish- 
grey with a green- 
ish tinge, spotted 
with brown and 
the tentacles flat, 
triangular and 
have a backward 
trend. It is ovi- 
parous and the 
70 to 150 eggs, 
deposited at in- 

FIG. 163. Niagara Snail, Lymnaea stagnalis. 
tervals in cylindrical capsules, hatch in15 to 20 days. ‘This is one of the 
most handsome snails, of which a pair or two may be kept in the aquarium 
without damage to the plants. Its range is over the entire northern latitudes, 
and in the United States is found from Vermont through the Northern tier 
of States to the PacificOcean. Itis popularly known as the ‘Niagara Snail.” 
L. palustris, Fig. 164, is a destructive though interesting common 
snail found in nearly all ditches, ponds and streams in the Eastern Atlantic 
slope and in Europe. The conical shell is 34 to 114 inches long, of a light 
horn-color on the body 
whorl and usually a 
dark horn-color, brown 
or black above. It has 
five or six whorls sep- 
arated by white lines, 
with the body whorl 
half as longasthe shell. 
The ovate aperture is UC as Mtg LAE 
nearly as long as the body whorl and the suture is deeply depressed. The 
body is dark gray or nearly black, with a violet tint, faintly spotted with 
yellow and black, and the tentacles flat and conical. It ranges from New 
England through Pennsylvania and south. Its habit of coming above the 
water serves as an identification in the aquarium, into which it is sometimes 
introduced with aquatic plants. The 60 to 80 eggs are deposited in a 
cylindrical capsule and hatch in 12 to 20 days. 
L. columella, Fig. 165, has an ovate thin and fragile 5¢ to 34 inch long shell 
of four whorls crossed by minute lines of growth. The suture is deeply im- 
pressed and conspicuous, the spire narrow and the aperture larger than 
half the length of the shell. The body whorl is large and expanded, and the 

231 
