On the Variation of the Genus Arion, Fér. 307 
Fig. 4, Bythocypris? cuneola, J. & K., var. Carapace, showing right 
valve. 
Fig. 5. Bairdia curta, M‘Coy. Carapace, showing right valve. 
Fig. 6. Bairdia subelongata, J. & K. Carapace, showing right valve. 
Fig. 7. Bairdia plebeia, Reuss. Left valve. 
Fig. 8. Bairdia plebeia, Reuss, Cuarapace, showing right valve, 
Fig. 9. Bairdia brevis, J. & K. Left valve. 
Fig. 10. Bairdia amputata, Kirkby. Carapace, showing right valve. 
Fig. 11. Bairdia ampla, Reuss. Left valve. 
Fig. 12. Bairdia grandis, J. & K. Carapace, showing right valve. 
Fig. 18. Bairdia Hisingeri? (Miinster), var. Mongoliensis, noy. Cara- 
pace, showing right valve. 
.XLVII.—WNotes on the Variation of the Genus Arion, Fér. 
By Watrter K. Couiinae, Assistant Demonstrator in 
Zoology, St. Andrew’s University. 
THE diversity of opinion that 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, Fér., 
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. Bocaget. From the descriptions 
below it will be seen that these variations are so slight 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. Scharff * 
and at Guernsey by Mr. Brockton Tomlin f. 
Arion emptricorum, Fér. 
Var. Bocaget, Simroth.—Sides blackish, back decidedly paler 
or white. Portugal. 
Subvar. nov.—Sides blackish, back grey ; margin of sole light 
yellow. Ireland (Scharf’). 
Subvar. nov.—Sides blackish, back light bluish grey ; foot 
whitish, margin of sole white. Yorkshire (Collinge). 
* Trans. Roy. Dublin Soe. vol. iv. ser. ii. p. 560, pl. lvi. fig. 16. 
+ ‘British Naturalist,’ p. 46 (1891). 
