Shells of Common Occurrence. 139 



mucous thread to descend. The spotted grey slug 

 (L. cinereus), best known as the black slug, but 

 not to be confounded with the Arion, though less 

 common than the field slug, is very abundant in 

 damp situations, under decaying wood and frag- 

 ments of stones in gardens, hedges, etc., and in 

 cellars and outhouses ; copious rain, or even dew, 

 enticing it from its retreat. It is the largest of 

 the slug family, being six inches long, and will 

 be found handsomely formed when attentively 

 surveyed. It is circular on the back, acute and 

 pointed at the tail; with upper tentacles of great 

 length and short lower ones ; it secretes colourless 

 mucus. The shield is slightly stained with pink. 

 It deposits during spring from fifty to sixty eggs, 

 attached in heaps together, under stones and at 

 the roots of grass and trunks of trees. 



The Helix, or snail, has a shell spirally rolled, 

 and although possessing no operculum, it sub- 

 stitutes that filmy mucous covering, by means of 

 which it closes up its shell, and which is perforated 

 with holes to enable it to breathe. Eemaining 

 concealed in obscurity during the day, it comes 

 forth to feed evening and morning, or after rain, 

 retiring from business altogether in the winter into 

 a hole or crevice, or amongst moss, and shutting 



