x MOLLUSC A 137 



at the hind end of the very long body. The yellow-brown 

 body is marked by two conspicuous lateral grooves for 

 disseminating mucus ; unlike other snails its body is narrowest 



FIG. 88. The Carnivorous Slug (Testacella). 



in front and broadest at the hind end. This slug lives largely 

 underground, and in cold weather forms a kind of cocoon of 

 slime and earth. The eggs are laid singly, instead of in 

 clusters as in most slugs. Each egg is about ^th of an inch 

 across. 



Classification of the Univalve Molluscs mentioned in Chapters 

 IX. and X. 



Order I. PULMONATA. Those breathing with a "lung"; 



hermaphrodite forms. 

 Sub-order 1. Basommatophora. Water snails in which the 



eyes are at the base of the non-retractile tentacles. 

 Family 1. Limnaeidae. Water snails with fragile dextral 

 shells in which the lung-sac is protected by 

 an external lobe of the mantle. 

 Limnaea, the Common Pond Snails. 

 Planorbis, the Trumpet or Flat-coiled Snails. 

 Ancylus, the Hooked Snails or Fresh- water 



Limpets. 



Family 2. Physidae. Water snails with siriistral shells, 

 over the margin of which the mantle is 

 reflected. 



Physa, the Thread-spinning Snails. 



Sub-order 2. Stylommatophora. Land forms with two pairs 

 of hollow retractile tentacles, and with an eye at the tip 

 of each of the upper pair. 



