210 MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 
Arion hortensis Férussac. 
1819 Arion hortensis Férussac, Hist. Moll., p. 65, pl. 2, ff. 4, 5. 
1826 — lineatus Risso, Hist. Nat. Eur. Merid., p. 55. 
1855 — (Prolepis) fuscus Moq.-Tand., Hist. Moll. France, p. 14, pl. 1, ff. 28-30. 
1866 — anthracius Bourg., Moll. nouv. lit., ete., p. 178, pl. 29, ‘ff, 8-10. 
1870 — pelophilus Mabille, Ann. Malac., p. 117. 
1870 — distinctus Mabille, op. cit., p. 119. 
1881 — pyrenaicus Fagot, in Gourdon. Moll. Luchon, p. 82. 
1883. — alpinus Fitz., Syst. Verz. Oesterr. Weichth. 
1889 — cottianus Pollonera, Contr. Studio Arion Europ., p. 14, ff. 23, 24. 
1894 — elongatus Collinge, Ann. and Mag. Nat. Hist., p. 66, pl. 5a. 
1897 — ceruleus Collinge, Proe. Zool. Soc., p. 444, pl. 31, ff. 18, 19. 
1821 Limax subfuscus Pfeiffer, Syst. Anord., p. 20. 
1868 Prolepis hortensis Malm, Limae. Scand., p. 49, pl. 2, f. 5. 
1873 Kobeltia hortensis Seibert, Nachr. Deutsch. Mal. Ges., p. 81. 
ISTORY.— Arion hortensis (hor- 
tensis, a garden) was first found 
in this country in 1817, ‘i Dr. Leach, 
who placed specimens in the National 
Collection ; its occurrence was, how- 
ever, not published until 1821, when 
Dr. Gray added the species to the 
British list in the pages of the 
Medical Repository. 
It is probably in part the Zimar 
Fasciatus of Nilsson, and according to 
Férussac the vestigial shell is “the 
Limacella concava of Brard. 
This species has been separated 
from Arion ater and A. subfuscus by 
Moquin-Tandon and other s,and placed 
ina group Prolepis, which is chavacter- 
ized by possessing a more completely 
formed shell than is said to be present 
in the two former species. ‘This 
character is, however, quite illusory, 
o. ie as 1s also their separation based upon 
¢ VLR the modification of the genital atrium, 
as proposed by Dr. Simroth. 
This species is associated with Mr. E. J. Lowe, F.R.S., of Shirenewton 
Hall, Chepstow, the famous fern specialist, and author of many esteemed 
works thereon, in acknowledgment of the excellence of his ‘‘Conchology of 
Nottingham,” published in 1853, and of his exceptional knowledge of the 
specific characters and habits of our British slugs. 
Diagnosis.— Arion hortensis may be distinguished from Arion ater 
and Arion subfuscus by its much smaller size and different shade of 
colouring. From Arion circumseriptus it is separable by its tough, 
leathery integument, its more slender form, orange foot, black dorsum, 
and the more indistinctly defined black lateral bands, which are also 
less dorsally placed than in that species. 
