62 COLLINGE : REVIEW OF THE ARIONID^ OF THE BRITISH ISLES. 



Arion lusitanicus, Mabille. 

 = A. rufus, Morelet, Descr. d. Moll. Port., 1845. 

 It may be questioned by some whether this form is distinct enough 

 to rank as a species. As yet, I have only seen very few specimens, 

 but both Simroth (41) and Pollonera (30) recognise its specific rank. 

 Both of these authors have figured it and its various colour variations. 

 Pollonera's figures represent such forms as I have seen (30, pi. ix., 

 figs. 1 — 4), a number of Simroth's figures represent young examples. 



Arion subfuscus, Drap., 1801. 

 Body yellowish or greyish-yellow ; mantle generally covered with 

 a reddish-yellow mucous ; head and tentacles greyish ; sole 

 white, yellowish or grey ; foot-fringe white or light-yellow ; 

 lineoles grey; rugce short and flat; sulci blue; slime colourless. 

 For a long time this species was looked upon in this country as a 

 form of A. hortensis or the young of A. empiricorum. Cockerell (3) was 

 the first to separate it from these and rightly class it under this species. 

 The A. flavus of Miiller, is thought by Scharff to have been an 

 immature form of this species. Like A. empiricorum this species has 

 the foot-fringe transversely striated, and a dark head and tentacles. 

 The back and mantle are usually so largely covered by a thick orange- 

 red mucous, that the actual colour is at first doubtful. This mucous 

 secreted by the mucous glands of the integument and mantle, must 

 not be confounded with the slime, which is colourless. 



Anatomy. — The lower vestibule is proportionately much larger 

 than that of A. empiricorum, the upper one being absent. The 

 retractor muscle has its attachment to the oviduct, far removed from 

 the vestibule. The oviduct and prostate are comparatively short. 

 The vas deferens is long and tapering. Generally the receptacular 

 duct exhibits a slight dilatation previous to entering the lower 

 vestibule, differing in this point from the two preceding species. 

 The form of the reproductive organs in any but adult specimens, 

 is very difficult to diagnose. The absence of an upper vestibule and 

 the ] form of the oviduct, are perhaps the two most characteristic 

 features. Mr. E. W. Swanton recently sent me some Arions from 

 Southampton, which I thought resembled A. cottianus, Poll.; dissection, 

 however, did not support such a view. Simroth, who has seen a 

 dissection, writes me, saying, " I think it is a very developed 

 A. subfuscus, richly folded in the distal copulatory portion of the 

 oviduct." There were three specimens all alike and quite unlike 

 anything I have seen before in this species. 



Reproduction.- — The eggs which are deposited from June to 

 October average from 20 to 30 in number. They are transparent 



