On the Variation of the Genus Arion, FSr. 307 



Fiff. 4. Bythocypris ? cuneola, J. & K., var. Carapace, showing right 

 valve. 



Fig. 5. liuiidia arrta, M'Coy. Carapace, showing right valve. 



Fig. 0. Jiairdin suhvhmgatn, J. & K. Carapace, showing right valve. 



Fig. 7. liairdia plcbeia, Ivtuiss. Left valve. 



Fig. 8. liairdia plebna, Itcuss. Carapace, showing right valve. 



Fig. 9. liairdia brevis, J. & K. Left valve. 



Fig. 10. JJairdia ain/iidafa, Kirlihy. Carapace, showing right valve. 



Fig. 11. liairdia anipla, Iveuss. Left valve. 



Fig. 12. liairdia grainlis, J. & K. Carapace, showing right valve. 



Fig. 13. liairdia Jlisi/igeri ? (Miinster), var. Mongohensis, nov. Cara- 

 pace, showing right valve. 



XLYH. — Notes on the Variation of the Genus Arion, Fer. 

 Y^J Walter E. Collinge, Assistant Demonstrator in 

 Zoology, St. Andrew's University. 



The diversity of opinion tliat at present exists as to specific 

 and varietal forms in this genus induced me some time ago 

 to collect a large quantity of the different species and varieties 

 from many parts of the country for careful comparison and 

 anatomical examination. Some Arion empiricorum^ F^r., 

 which are at present under observation, are of interest in that 

 they approach a Portuguese form described some little time 

 ago by Simroth, viz. var. Bocagei. From the descriptions 

 below it will be seen that these variations are so slie-ht that 

 it would be absurd to name them individually ; and as they 

 are likely to occur elsewhere I now describe them, hoping 

 thereby to save future collectors from adding to an already 

 overburdened nomenclature. 



The specimens I have were collected in Yorkshire ; but 

 allied forms have also been found in Ireland by Dr. Scharfif* 

 and at Guernsey by Mr. Brockton Tomlin f. 



Arion empiricorunij Fdr. 



Var. Bocagei, Simroth. — Sides blackish, back decidedly paler 

 or white. Portugal. 



Subvar. nov. — Sides blackish, back grey ; margin of sole light 

 yellow. Ireland [Scharff). 



Subvar. nov. — Sides blackish, back light bluish grey ; foot 

 whitish, margin of sole white. Yorkshire {Collinge). 



* Trans. Roy. Dublin Soc. vol. iv. ser. ii. p. 560, pi. Ivi. fig. 16. 

 t ' British Naturalist,' p. 46 (1891). 



