MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA, Lay 
Milax sowerbii (Férussac). 
1823 Limax sowerbii Férussac, Hist. Moll., Suppl., pl. 8p, f. 7, p. 96 ¢. 
1826 — _  carinatus Risso, Hist. Nat. Moll. Medit. 
1852 — _  carinatus Leach, Moll. Gt. Brit., p. 54, pl. 8, f. 3. 
1856 —  argillaceus Gassies, Act. Soc. Linn. Bord., p. 232. 
1862. — marginatus Jeffreys, Brit. Conch., p. 132. 
1831 Limacellus unguiculus Turton, Manual, p. 25. 
1855 Milax sowerbyi Gray, Cat. Pulm. Brit. Mus., p. 175. 
1896 Amalia sowerbyt Adans, Man. Brit. Land Freshw. Shells, p. 32, pl. 1, f. 10. 
ISTORY. — Milax sowerbii was 
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. 
Milax sowerbii was, however, prior to 
that date, carefully figured ‘and de- 
scribed by eae from specimens 
sent from the neighbourhood of Lon- 
don by Mr. G. B. Sowerby, to whom 
he dedicated the species. 
The name sowerbii is adopted for 
our British form in the belief that the 
Limax marginatus of Draparnaud is 
not identical with our species. 
With this species the distinguished 
Italian limacologist, Signor Mario 
Jar ce ae clone Lessona, is 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 authoritative and 
standard publications upon the European slugs. 
Diagnosis.—ExtTEeRNALLY, Milux 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 rugee, 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 M7. gagates is quite globose. 
Description.—ANIMAL laterally compressed, with its height little exceeded by 
its length when contracted, but reaching to 75 mill. or more in length when adult 
and fully extended ; the BODY is comparatively dry and furrowed on each side by 
about fourteen longitudinal grooves, parallel with the keel, but sometimes forking 
backwards, and connected by numerous transverse channels which form a flat 
tubereulation ; it is typically of a grey ground colour, but a yellow shade is given 
to the body owing to its being closely and. densely beset with or! ange-coloured specks, 
which become sparser towards the foot- margins ; the usual darker aspect 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 
Nn A re | {) M 
