COLLINGE : REVIEW OF THE ARIONIDyE OF THE BRITISH ISLES. 57 



Sittingbourne, Kent, who has devoted much time and care on my 

 behalf to the Arions of the S. and S.W. of England, forwarding 

 continual supplies ; to Dr. Heinrich Simroth I am also much 

 indebted for very kindly examining doubtful or perplexing 

 forms, &c. ; and to Signor Carlo Pollonera, of the Museum of 

 Zoology and Comparative Anatomy of the Royal University of Turin, 

 for examples of Italian and French Arions, &c. 



INTRODUCTORY. 



The Arionidce are a family of slugs distributed throughout the 

 E. and W. Hemispheres, the different sub-families, genera and species 

 of which have engaged the attention of anatomists, malacologists, 

 and collectors of almost every school. Prominent among such we 

 find the names of Ferussac, Blainville, Nunneley, Platner, Jourdain, 

 Garnault, Simroth, Pollonera, Lessona, Binney, Heynemann, Morch, 

 J. G. Cooper, Godwin- Austen and others. 



The known genera may be conveniently grouped under four sub- 

 families, viz. : — 



1. Phil my ci nee. 3. Bintieyince. 



2. Arionince. 4. Oopeltince. 



Until more systematic and minute anatomical investigations have 

 been made upon a many of the genera of these sub-families, but 

 little can be said respecting their affinities. The second family 

 having come more directly under my own observations, as embracing 

 all our British forms, is the one whose anatomy I am more particularly 

 acquainted with. I agree with Scharff (36) who has very conclusively 

 shown that there is no ground whatever for including the genera 

 Avion and Geomalacus under the Helicidce ; Cockerell (5) considers the 

 Arionidce more closely related to the Helicidce than to the Limacidce. 

 While these last two families have many points in common, I know 

 of no observations that have demonstrated any marked relation in 

 either of them to the Arionidce. 



As previously stated, the Arionidce at present known to the 

 British Isles, are all members of the sub-family Arionifice, and may 

 be grouped in two genera, viz., Arion, Fer., and Geomalacus, Allman. 

 Both of these genera are characterised by the presence of a mucous 

 gland at the caudal extremity of the body. While such a feature, 

 at present, is characteristic of both of these genera, it cannot be said 

 to be so of the sub-family, for in the genus Anadenus, Heyne, it is 

 absent. Seeing that it is also present in certain Limacidce, it cannot 

 be looked upon other than a minor generic distinction. Mr. Cockerell 

 (4), whose classification I give below, recognises seven true and two 

 doubtful genera, viz. : — 



