UMAX. 85 



band ; shield concentrically wrinkled ; slime viscid, yellowish. 

 Length, cr/S 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 Allansford, 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 1 500 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. 



