ARION ATEE. 175 



The A. empiricorum is considered as chiefly "West European and to be 

 the form inhabiting this country. It is noted as mainly characterized 

 by its very short and insignificant lower vestibule and the large and wide 

 upper section, an enlargement due to the swollen outlets of the organs 

 debouching therein. 



A. ater is said to be confined to North-eastern Europe, and has been 

 described as differing by its larger size and in possessing a thick and 

 swollen lower vestibule, while the upper section is less noticeable owing 

 to the undeveloped state of the oviduct and other outlets. 



These differences are, however, little more than individual, local, or 

 seasonal variations in the development of the different organs, as is affirmed 

 by Dr. Babor, who shows that the varied development of the atrium is 

 merely the expression of sexual phases, while Signor PoUonera has con- 

 clusively demonstrated the unreliability and fugitive character of the 

 vestibular modifications and their unsuitability for specific differentiation 

 in Arion. 



VARIATIONS IN COLOUR OF ANIMAL. 



Var. atra L., Syst. Nat., ed. x., 1758, p. 652. 



The strict type of this species is undoubtedly the black or blaclcish form, with 

 the median area of the foot-sole markedly paler than the side zones. It has, however, 

 had a number of special names devoted to it by various observers and is probably : — 



Liviax ater L., op. cit. 



Arion empiricorum aldrffvandii Kalenicz., Bull. Mosc, 1851, p. 113. 



Arion rufus ^ ater Moquin-Tandon, Hist. Moll. France, 1855, ii., p. 10, pi. 1, f. 20. 



Arion {Lintax) ater var. niger Dum. & Mort., Moll. Savoie, 1857, p. 6. 



Arion rufus var. nigya Baudon, Journ. de Conch., 1881, p. 196. 



Arion empiricorum var. maurus Held. 



The distribution of this form is almost universal in this country, as it is one of 

 the variations more especially evolved by our cool and moist climate. 



On the continent, this form is found in Germany, Holland, Belgium, France, 

 North Spain, Portugal, Norway, up to 66° 49' north latitude, South Sweden, Den- 

 mark, Austro- Hungary, Switzerland, and North Italy. 



Var. aterrima Taylor. 



Body, shield, and creeping disc uniformly black. 



It is desirable to discriminate from the ordinary form the jet-black individuals, 

 in which the black pigment has also overspread the whole surface of the creeping 

 disc. This variety is not common, and would seem to be more especially a northern 

 or mountain form, as its occurrence in other places seems to be more or less sporadic 

 or casual. Mr. Welch and Mr. Praeger, in Oct. 1897, found some very characteristic 

 examples on the summit of Slieve-Donard at an altitude of 2,796 feet. 



It is not improbable that Arion hispanicus of Simroth, which is characterized by 

 its smaller size and uniform black body and creeping disc, belongs to this variety. 



Many authors describe variations of this species as aterrimus totus, but it is not 

 by any iaieans clear that the descriptions were intended to apply to the foot-sole as 



well as the body. 



ENGLAND AND WALES. 



Devon N.— Ilfracombe, July 1904 ! R. Leach. 



Huntingdon— Garden, Huntingdon, Sept. 1904 ! Miss Emily M. Foster. 



Gloucester E.— Cirencester, Aug. 1904 ! Mrs. Blundell. 



Merioneth — Hills above Barmouth, alt. 2,000 feet, Aug. 1884 ! J. Hopkinson. 



Lincoln N.— Rippingale, Sept. 1904 ! H. Preston. 



Cheshire— Garden, Broad road, Sale, May 1885 ! C. Oldham. 



Lancashire W.— Over Wyresdale, alt. 1,000 ft., April 1903 ! Rev. W. ^Y. Mason. 



York N.E.— Bunswick Bay, June 1885 ! W. Denison Roebuck. 



York Mid W.— Summit of Oughtershaw Moor, Wharfedale, Aug. 1904 ! W. 

 Denison Roebuck. 



Durham— Croft, April 1887 ! and near High Force, June 1884 ! Baker Hudson. 



Westmorland- On the summit of Coniston Old Man, alt. 2,660 feet, July 1887, 

 S. C. Cockerel!. Grange-over-Sands, July 1904 ! W. J. Davey. 



Cumberland— Salkeld Dykes, Penrith, July 1904 ! H. Britten. Scafell Pikes, 

 alt. 3,000 feet ! W. West. 



