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Show 1891.] GEOGRAPHICAL DISTRIBUTION OF SLUGS. 221 Arionince. There are seven recognizable genera in this subfamily. Arion, with numerous described species, is confined to the European region, except that species have been introduced by human agency into North America, N e w Zealand, and St. Helena. The St. Helena species is A. hortensis, Fer. ; six specimens from this locality are in the British Museum, collected by M r . A. E. Craven. The N e w Zealand species was described as a new species, A. incommodus, Hutton; but a specimen in the British Museum from Dunediu (Otago Univ. Mus.) shows it to be the cinereo-fuscus form of A. subfuscus, Drap. The genus Arion also occurs in Madeira and the Azores, where it has some appearance of being native, though none of the species are peculiar. There are two specimens of A. subfuscus from Madeira in the British Museum (Mr. Mason), and A. empiri-corum, Fer., has been recorded from there. Among the Azores species there is, according to Simroth, a small insular variety of A. lusitanicus, Mab. Ariunculus, Lessona, is a small genus of the Mediterranean region, with one species in Sardinia, and three in Piedmont. One of the latter is also found in the Dept. of Var, in S.E. France. Geomalacus, Allmati, with its subgenus Letourneuxia, Bgt., has nine supposed species, found in different parts of Portugal and Algeria, with one species at the Straits of Gibraltar and another in Co. Kerry, Ireland. The distribution of the Irish species, G. macu-losus, is very interesting, as it seems to be confined to a small district in S.W. Ireland, and Portugal, though it has been reported also from N.W. France. It is also worthy of notice that in the more northern part of its range the genus shows a strong tendency to lose its bands and become dark with pale spots, while the southern species are very distinctly and invariably dark-banded. Tetraspis, Hagenm., an extraordinary genus with a mantle-aperture, from Carniola, may safely, I think, be put on one side, because Hagenmiiller's description and figure seem to belong merely to a specimen of Arion allied to hortensis, with an artificially-made hole in the mantle! The flexion of the mantle-bands does not prove the hole to be normal, as A. alpinus} which has no mantle-aperture, has them strongly curved outwards much as in Tetraspis. Aspidoporus, Fitz., 1833, from Austria, is another supposed genus with mantle-aperture, founded really on a species of Amalia l. The next genus of the subfamily is met with in the far-distant Himalayas, namely, Anadenus, Heynem. For an account of the species see Ann. Mag. Nat. Hist., Oct. 1890. There are six described species, some of them of great size. From the Himalayas eastward there are no other Asiatic representatives, the subfamily being, so far as is known, entirely absent in the Chinese, Malay, and Australian regions. It is also absent in South America, and in all parts of North America except the Pacific region, where it is largely developed, with three distinct genera. Ariolimax, Mdrch, containing some 1 See Heynemann, Jahrb. d. mal. Ges. 1884. |