LIIflfEAN SOCIETY OF LOXDOX. 7 1 



The tracks of these two species, H. aspersa and Limax maximus, 

 agree iu being formed of a series of pointed impressions disposed 

 in curved rows, sometimes mailing a zigzag, wliere the mollusc has 

 advanced more or less regularly and at an even pace ; at other 

 times mixed up, where the mollusc has moved irregularly or has 

 crossed its own track. Each point represents a lick of the radula, 

 and where the animal has not entirely cleared off the whitening, 

 patches are visible, with the aid of a magnifier, covered with very 

 line parallel grooves which are evidently impressions of the in- 

 dividual teeth. The outline of the imprint of the radula is also 

 sometimes seen to be very minutely serrated. Another feature 

 is observable, namely, the existence of short scratches in the 

 whitening in advance of the point, varying from one to three in 

 number. They greatly resemble, iu miniature, the prints of 

 animals' claws in snow. 



The impressions of Limnx maxwms may be distinguished from 

 those of U. aspersa in being smaller, moi'e sliarply pointed, and 

 in the example exhibited they are more crowded, this however 

 may not be a constant characteristic. The scratches also differ ; I 

 have not observed more than two in Limax maximus, and they are 

 detached from the main impression, whereas in H. aspersa they 

 are united to it and occasionally there are three. The detachment 

 may possibly arise from the radula of the slug not having 

 penetrated so deeply into the whitening as that of the snail ; or 

 the coat of whitening may be thicker or harder. 



The following observers have recorded feeding-tracks of Gastero- 

 poda. Ebenezer Emmons in 1846 ('Agriculture of New York,' 

 vol. i. p. 68, pi. xiv. fig. I) described and figured some tracks on 

 fine green slate which he at first mistook for fossils. Prof. E. B. 

 Poultou in 1885 published an account (' Nature,' vol. xxxiii. 

 p. 176) of snails eating the whitening upon a greenhouse roof. 

 He did not see the animal at work, but thought it was almost 

 certainly Helix aspersa. Mr. Woodworth in 1893 (' Science,' 

 vol. xxi. p. 157) described some tracks of snails, of which he did 

 not give the name, on carboniferous rock. Herr Eathay in 1898 

 (' Zeitschrift fiir Pflanzenkrankheiten,' B. viii. pp. 129-133) figured 

 and described tracks made by Helix hortensis when feeding on 

 Pleurococcus vulgaris growing on the bark of trees. 



The most detailed account, however, is that of Mr. B. B. Wood- 

 ward, in 1906 (Proc. Malac. Soc. March, p. 31, figs. 1 & 2), of 

 impressions made by an unnamed slug upon an overexposed 

 photographic print. The mollusc had eaten quite through the 

 gelatine, exposing the white paper, which retained not only the 

 coarser markings, but also the tine striae made by the individual 

 teeth similar to those referred to above. The figures of the tracks 

 of this slug much more nearly resemble the tracks of L. maxhmis 

 then of H. aspersa. I have not, however, seen any notice of the 

 fine scratches. 



Prof. Poulton suggested that snails eat the whitening on account 

 of carbonate of lime being requisite for diff^erent parts of their 



