MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSOA. 



151 



Milax sowerbii (Ferussac). 



1823 Liinnx sowerbii Fenissac, Hist. Moll., Suppl, pi. SD, f. 7, p. 96 _(. 



1826 — carlnatus Ri.sso, Hist. Nat. :Mo11. Meilit. 



1852 — carinatuv Leach, IMoll. Gt. Brit., p. 'A, pi, 



18.56 — arcjillaceus Gassies, Act. .Soc. Linn. Lurd. 



1862 — mnrginatus Jeffreys, Brit. Conch., p. 132. 



1831 Lliimcellus ■unriniculua Turton, Manual, p. 2."). 



185.5 Milax mwerbi/i Gray, Cat. Pulm. Brit. Mus., |). 175. 



1896 Ainalia sower'byi Adams, Man. Brit. Land Frcshw. Shells, p. 32, pi. 1, f. 10. 



pi. 8, f. 3. 

 p 232. 



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A/i^ 



c/ey^ 



■pr.je<. — . 



IJISTORY. — Mfer $owerbii wa.s 

 -'■-■■ probably first described by Leach, 

 but his description and figure, though 

 privately circulated, were not actually 

 published until 1852, at which date 

 Dr. J. E. Gray edited and issued the 

 work Leach had in great part prepared. 

 MUii.r sfurerb'ii was, however, prior to 

 that date, carefully figured and de- 

 scribed by Fcrussac from specimens 

 sent from the neighbourhood of Lou- 

 don by ^L'. G. B. Sowerby, to whom 



f? ^^■Bfta*^' ■' ''-**'SHIt^ he dedicated the species. 



^ ^^^BS^yi'^W ■"' :MM wu^. The nanre sowerbii is adopted for 



our British form in the Ijelief that the 

 Limax marginatum of Lraparnaud is 

 not identical with our species. 



With tliis sjiecies the distinguished 

 Italian limacologist, Signer Mario 

 Lessona, i.s associated, as a mark of 

 appreciation of his malacological labours 

 and more especially in recognition of the sterling merits of the important 

 work, "Monographia dei Limacidi Italiani," written in collaboration with 

 Signor Pollonera, which is undoubtedly one of the most autlioritative and 

 standard publications upon the European slugs. 



Diagnosis. — Extern.vlly, Mila.r sowerbii may be distinguished from 

 M. gagates by the prominent keel being usually markedly paler than the 

 general colour of the body, and most strongly accentuated on the back ; 

 the body sculpture also shows distinct though flattened rugre, with their 

 interstices more or less marked by black or blackish pigment. 



Internally, it is easily separable from its congener, by its long and 

 tapering spermatheca, an organ which in 31. gagates is ({uite globose. 



Description. — Animal laterally compressed, with its hei^dit little exceeded Ly 

 its len,i,'th when conti-acted, hut reaching to 75 mill, or more in length M'hen adult 

 and fully extended ; the body is comparati\'el3' dry and furrowed on e.ach side by 

 about fourteen longitudinal grooves, parallel with tlie keel, lint sometimes fnrking 

 backwards, and connected by numerous transverse channels which form a Hat 

 tuberculation ; it is typically of a grey ground cohnir, but a yellow shade is given 

 to the body owing to its being closely and densely beset with orange-coloured specks, 

 which become sparser towards the foot-margins ; the usual darker as|)ect of the 

 animal is due to the back and sides being closely besprinkled with black, the dots 

 being less numerous towards the sole, but more closely aggregated in the interstices 



