38 1 kil) I lljol- OKI. AND. M.-X. Kl. 



far as to the line corresponding to the outer limit of the orange bands in 

 var. circumscripta : the lower j^art of the sides paler. Otherwise it looks 

 like var. circiiinscripid ; the meflian row of p.ile tubercles as usual is most 

 distinct in the contracted animal. 



The reproductive organs proved to be in a rudimentary condition, but 

 the pointed bladder of the receptaculum could easily be distinguished. 



A single specimen, about 3,5 cms. extended, was found in the garden 

 of the zoological Museum at Toicn, Kristiania; I collected it in a heap of 

 decaying leaves, together with var. circnui^cripta. 



Very often it will be a matter of judgment as to whether a form is to 

 be designated as a variety or an aberration. Following the definition of 

 Plate:' „eine seltene, stark abweichende Variation, häufig mit patholog. 

 Anstrich", I am of opinion that in this case it will be most correct to 

 speak of an aberration. The pathological factor is obvious, not only in the 

 total absence of dark pigmentation, but also in the rudimentary repro- 

 ductive organs. 



Distribution. Owing to confusion with other species, especially with 

 Arion hoiioisis, the distribution is difficult to decide; in several coun- 

 tries the statements of its occurrence are doubtful. The most northern 

 locality is 69° N. L, (Kinn, Kvæfjord on Hinno, where it was collected for 

 me by my friend stud. real. Birger Bergersen), and towards the south it 

 extends to the Pyrenees and the Alps. It is stated to occur as far as to 

 the Ural mountains in an eastern direction ; at any rate it occurs in the 

 neighbourhood of Moscow (Simroth i 901). 



In Sweden the species is found in the southern and the middle 

 counties as far as 64° N. L. (under the name of Arion /larfc/isis), and it is 

 very common throughout Denmark. It occurs in the south of F' inland 

 and at any rate in Western Russia; in Germany and Austria-Hun- 

 gary it is recorded in scattered localities, and according to Simroth (1890) 

 in Transylvania, being more commonly found in France and especially 

 in the British Isles. It has been found in the Faroes, and has been 

 introduced by man in some places in North America. 



In Norway it is chiefly restricted to the coast, almost all localities 

 being situated from the vicinity of the Kristiania and Drammenstjord to 

 Hinnø (map 3). 



With regard to the vertical distribution, the greatest elevation at which 

 I have found it has been at Tinnoset in Telemarken, about 200 m. above 

 sea level. 



Bionomics. Though Arion circiimscriptiis may be found together with 

 Arion siibfusciis, yet as a rule these two commonest of the smaller Nor- 

 wegian species avoid each other. Indeed, A/'ion circiinisciiptiis prefers 



' „Prinzipien der Systematik mit besonderer Berücksichtigung des Systems der Tiere , 

 in Kultur der Gegenwart, Teil III. Abteilung IV, 4. 



