'4 



FKIUTHJOF ØKLAND. 



M.-N. Kl. 



forms the lower part ol" the sides, limited dorsally by the pedal furrow, 

 is very conspicuous and presents a system of transversal furrows every 

 other one of which is darker tlian the intermediate one. The tubercles of 

 the skin, too, are peculiar, being longer than in other Norwegian species, 

 and in contracted specimens often keeled in such a manner that a trans- 

 verse section would nearly represent an equilateral triangle. This applies 

 especially to the tubercles close behind the shield in the living animal. 



As regards the colour only a little can be said of general interest. 

 The colour is usually uniform and the most common Norwegian variety 

 is die black var. atra. But various types of the whitish var. alba are 

 relatively frequent, though in smaller numbers. As a rule the shield-bands, 

 prevalent in most Arions, are absent. They sometimes appear in the young, 

 and are then very characteristic, bending anteriorl}' towards the mid-line of 

 the shield, here nearly presenting two parallel lines. As far as I have been 



Fig. 5 — 6. Jaws oi Arioii (iter, -^l. 



able to ascertain, this is a most characteristic character when present, and 

 notice may be taken of the fact that the shield-bands may even persist in 

 the adult, with just the type described (var. fasciata \'ax den Broeck, 

 Mem. Soc. Mai. Belg., 1869, pag 86). This variety, however, has not been 

 found in Norway. 



The mucus is generally colourless and of considerable tenacity. It 

 sticks to the fingers like glue. 



Internal characters, in the chapter concerning the genus these 

 have been described and depicted as a type. In the present section the 

 characteristics of the species will be mentioned. 



The jaw (fig. 5 — 7) is ca. 3 mill, broad in adults, and of a semi-lunar 

 form, seldom with the middle of the concavity slightly convex. Colour from 

 dark brown to black, but paler in the upper, convex part, the transition 

 to the darker part being more or less marked. There is often to be seen 

 a line conforming with the cutting edge, the line of attachment for the 

 elasma, /. e. the plate of suspension. 



Further the sculpture of the jaw varies greatly, so much so that is 

 almost impossible to find two which are exactly alike. Slender and broad 

 ribs alternate in a multitude of combinations; ribs which are more or less 

 distinctly divided into two or three are often to be seen. The number of 



