INTRODUCTION. XVli 
and in the same list includes “Arion subflavus” without description, in 
addition to Avion ater, thus ignoring not only Arion hortensis but his own 
Arion circumscriptus. 
In 1840 Dr. Gray published his so-called new edition of ‘lurton’s 
Manual, in reality a new work, and in this he sank Arion circumscriptus 
and Testacella scutulum as being but slight varieties, and also excluded 
T. maugei as non-indigenous. 
But in the same year, 1840, a new enthusiast and very capable investi- 
gator appeared, who may be regarded as our first British limacological 
specialist. ‘The Rev. B. J. Clarke took up the detailed study of the Irish 
slugs, and in the “ Annals and Magazine of Natural History ” for 1840 
and 1843 he established the existence of two new British species of which 
there had not previously been any indication in our literature : 
12. Limax arborum. 
13. Milax gagates. 
His papers also include indications of Avion subfuscus and Limaa cinereco- 
niger, as well as show that the author was aware of the presence in Ireland 
of Ariun circumscriptus and Testacella maugei, although he did not venture 
to reinstate them as species. 
In the same year, 1843, Limax arborum is first mentioned as Scottish 
in Macgillivray’s “History of the Molluscous Animals of Aberdeen, 
Kincardine, and Banff.” 
In 1842 an important discovery was made by Mr. W. Andrews in the 
form of the remarkable new slug, which in 1848 Dr. G. J. Allman described 
with a full anatomical account as 
14. Geomalacus maculosus. 
In 1848 Mr. Joshua Alder’s “Catalogue of the Mollusea of Northumber- 
land and Durham” was published in the 'l'yneside Field Club ‘Transactions. 
It is a work of great importance to us, as in it were brought forward two 
species new to Britain : 
15. Arion intermedius, 
16. Limax tenellus, 
and there is also a distinct reference to the slug we now know as Arion 
subfuscus. 
These additions mark the close of the earlier periods of the active 
scientific investigations of our British slugs, for although malacologists 
generally were by no means inactive, and numerous manuals were pub- 
lished including those of Brown in 1845, Leach in 1852, Forbes and Hanley 
in 1853, Gray’s Turton in 1857, Jeffreys in 1862 and 1869, Reeve in 1863, 
