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 -J-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. Lininaeidae. 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 sinistral shells, 

 over the margin of which the mantle is 

 reflected. 

 Physa, the Thread-spinning Snails. 

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

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

 of each of the upper pair. 



