THE LAND AND FRESHWATER MOLLT7SCA OF DORSETSHIRE. 97 



so, not ridged as in A.fluviatilis, greyish horn-colour; spi*-e near 

 the posterior margin, pointed and turned towards the left ; mouth 

 oblong. L.0.25. B.O.I. 



Hab. In slow rivers, marshes and ponds, on the underside of 

 the leaves of the water lily, and other aquatic plants, and on 

 fallen leaves of trees. On plants in the river Stour (T. Rackett^) ; 

 river Stour, Spettisbury ; Chamberlayne's, Bere Regis 

 (J.C.M.P.). 



TERBESTKIAL. 



This section of the Pulmonobranckiate order differs from the 

 previous one (whose aquatic habits require a branchial system 

 of respiration) in having a pulmonary system, analagous to 

 that of the vertebrates, also in the tentacles being retractile 

 instead of contractile and furnished with eyes on their summits. 



FAMILY I. LIMACIDJE. 



Genus I. ARION, Ferussac. 



Shell rudimentary, a calcareous plate, not spiral, concealed under 

 the mantle, and covering the respiratory cavity. Head prominent and 

 retractile, four retractile tentacles, the two upper ones furnished 

 with eyes. They are nocturnal in their habits, and are chiefly 

 herbivorous. They inhabit woods, gardens, and pastures. Some of 

 the Limaces occasionally climb trees and bushes, and suspend them- 

 selves by a glutinous thread. 



1. ARION ATER, Linn. 



Body contracted, asd rounded in front, pointed behind, varying in 

 colour, from black, brown, red, yellow, to almost white ; shield finely 

 shagreened, of a lighter colour than the rest of the body ; tentacles 

 nearly opaque, greyish-black, swollen at the tips, more so on the 

 lowes ones ; eyes on the summits of the upper tentacles ; Joot with a 

 yellow border, and black cross lines ; respiratory organs situated 

 towards the anterior margin of the shield, and on the right side. 

 L.4. B.0.5. 



Hab. Woods, hedges, fields, and damp places. Generally 

 distributed. 



