12 BRITISH MOLLUSKS. 



A very much smaller species than the preceding, more delicately 

 and more prettily coloured, occurring chiefly in the spring. The 

 body is more slenderly elongated than that of Avion ater, and the 

 wrinkled surface of the integuments is finer and partakes more of 

 the form of crowded leaflets. The shield is proportionately length- 

 ened, and it is rather more coarsely granulated. The typical 

 colour of Avion hortensis is a dark greenish-grey banded at the 

 sides with black, but it is extremely variable. M. Moquin-Tandon 

 describes and names as many as eleven varieties inhabiting France, 

 adopting the specific name offuscus, on the ground that the species 

 is the Limax fuscus of Muller. The descriptions of the Danish 

 author are extremely short, and, unaccompanied with figures, are 

 not easy to identify. The yellow variety (Limax flavus, Muller, 

 L. aureus ? Gmelin, Avion flavus, Ferussac) referred to in our re- 

 marks on the genus is believed by some collectors to be a distinct 

 species. Mr. E. J. Lowe informs me, that in specimens collected by 

 him in the vicinity of Nottingham he finds the back more rigidly 

 set, and the mucus orange-coloured. 



Avion hortensis has been transported to Boston, United States, 

 and become regularly acclimatized in the gardens and neighbour- 

 hood of that city. As an instance of the density of its integuments, 

 this little Arion may be distinguished from Limax when trodden 

 underfoot, a common fate of these mollusks, by its more leathery 

 toughness. 



Genus II. GEOMALACUS, Allman. 



Animal ; body lanceolate, subcylindrical, rather narrowly attenuated 

 posteriorly, margin of the foot brown, transversely grooved; head 

 with two pairs of tentacles, the upper pair much the longer, with 

 eyes at their extremity ; shield near the head, with the respi- 

 ratory orifice on the right side in front. 



Shell ; sobd, flat, subovate. 



This interesting form of slug was discovered about twenty years 

 since in comparative plenty in county Kerry, Ireland, and it has 

 not been collected in the British Isles in any other locaHty. It 

 differs in several anatomical particulars from its congeners. Its 

 more obvious peculiarities consist in the pulmonary sac and over- 

 lapping shield being situated near the head, as in Arion, with the 



