UMAX. 85 



band ; shield concentrically wrinkled ; slime viscid, yellowish. 

 Lengthy 0-75 inch. 



Shell irregularly oval or oblong, of a moderate consistence, 

 somewhat arched, partially tuberculous or beaded, microscopi- 

 cally and closely striated lengthwise ; boss indistinct, nearly 

 terminal ; margin rather broad, thin, and membranous. 



Habitat : North Mavine, Shetland, on stones in a 

 watercourse of a mountain mill. — B.C., vol. v. p. 156. 



This slug was first noticed in this country by Mr. 

 Blacklock, who found a single specimen in a wood 

 at AUansford, near Shortly Bridge, Northumberland. 



7. L. AR'BORUM,* BOUCHARD-ChANTEREAUX. 



PL. VI. bis. 



Body slaty-grey or greenish, spotted with yellowish-white, with 

 a dusky band on each side ; mantle rounded in front, bluntly 

 pointed behind, with rather fine concentric and longitudinal 

 wrinkles ; tentacles short ; back keeled near the tail ; foot mar- 

 gined with white ; slime colourless, abundant, and very tena- 

 cious. Length about 3 inches- 

 Shell nearly oval, flattish, glossy, thin, with a membranous 

 margin, indistinctly marked by the lines of growth, and micro- 

 scopically striate as in L. agrestis ; nucleus small, subter- 

 minal. 



Inhabits many parts of Great Britain, in woods, on 

 trees, especially the beech and walnut, it has also been 

 observed in exposed situations, and on rocks at an 

 elevation of 1500 feet. This species, especially when 

 young, is pre-eminently a thread-spinner ; it descends 

 and sometimes even ascends from one branch of a 

 tree to another by means of its mucous thread, which 

 is no thicker than that of a common spider. It may 

 be distinguished from the young of the next species 



* Frequenting trees. 



