518 ScHARFF — On the Slugs of Ireland. 



External characters. — I have attempted to use the markings of the mantle as a 

 method of readily distinguishing the species of Zimax, but there is another way, 

 though perhaps not altogether scientific, by which L. maximus can easily be iden- 

 tified. If the mantle be touched with a pencil or other sharp instrument, the front 

 portion curls round completely towards the source of irritation, whilst in the two 

 other species the same portion of the mantle will be only slightly lifted. Another 

 character by which L. maximus (excej^t in very dark specimens) can be distin- 

 guished, is a faint black line, running along the external margin of the foot, which 

 is quite absent in L. flavus and L. marginatus. Moreover, L. maximus is always 

 more slender, and its tentacles are almost double the length of those of L. mar- 

 ginatus, in specimens of the same size. The largest specimen I have met with 

 about Dublin, measured 110mm. long, and 9mm. broad; but I took one in May, 

 near Lough Caragh, Co. Kerry, which in spirit still measm-es 85 mm. by 14 mm. As 

 a rule, slugs shrink in alcohol to about one-half their length when alive and fully 

 stretched out ; but in this case I think the specimen can hardly have been more 

 than 150 n)m. long, which is exactly 6 inches. According to Moquin-Tandon (26), 

 they sometimes grow to the length of 170 mm. in France. 



We must not draw too rigid rules as to the limits of the specific characters of 

 this species, for it is subject to much variation in colour, though in Ireland it is by 

 no means the most variable of slugs, as it seems to be in Germany, according to 

 Simroth (38). 



All the specimens I have examined, whether they were of various shades of 

 gray, or of a dark brownish colour, were anatomically identical. Roebuck, in 

 his British Slug List (35), refers to Limax cinereo-niger (Wolff) as a form which is 

 found in Ireland, and which is now separated by the best Continental authorities 

 from L. maximus. He does not mention them, but Simroth (38), one of the best 

 authorities, certainly examined the form, and found it to agree with L. maximus. 

 Roebuck states, in the same Paper, that there are important differences between 

 the species in the genital apparatus, but he does not say what they consist in. I, 

 myself, have not had an opportunity of examining a specimen which could be 

 referred to this species, although I have had one or two, which were quite dark 

 above, but leaving the foot white.* 



The original lateral bands are always present in quite young specimens. On 

 the posterior third of the mantle they assume a horse-shoe shape without being 

 continued anteriorly. Curiously enough, in the adult, the left part of this horse-shoe 

 becomes almost always broken up into spots, whilst at the right side it generally 



* I haTe quite recently obtained a specimen at GlengariS agreeing in every respect with the description 

 given of cinereo-niger. On examination I found no difference anatomically between it and a typical 

 L. maximus, except in the origin of the retractor muscle of the penis. This confirms the opinion held 

 above that cinereo-niger can only be regarded as a variety of maximus. 



