280 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



second edition be useful — as the first has been and 

 still is — for ascertaining the number of species and 

 their local habitats; but it will also be of great 

 value for showing how much our knowledge, 

 especially of the local and general distribution of 

 species belonging to the different grouj)s, has been 

 increased within a definite period. 



Having devoted part of my leisure, during the 

 past year or two, to the working out of the distri- 

 bution of the Land and Fresh-water Mollusca about 

 Greenock, as well as in a few x^l^^^s beyond but 

 within easy access of that town, perhaps the result 

 of these researches, embodied in the following Notes 

 and List, may form a contribution — though possibly 

 not a very important one — to the second edition of 

 the Fauna and Flora referred to. 



Those who are studying this grouji of the Mollusca 

 will doubtless have noticed a growing tendency 

 among conchologists to be more and more discriminat- 

 ing. Differences in banding and coloration, as well 

 as in form, which used to be only incidentally referred 

 to in the description of the species, are being more 

 and more separated and raised to varietal or sub- 

 varietal rank; and considering the exceeding vari- 

 ableness of many species, it becomes to some extent 

 interesting to note the number and distribution of 

 the different varieties. This critical study of the 

 variations in different species may, if judiciously 

 carried out, be of considerable importance in increas- 

 ing our knowledge of the relationship of species ; 

 but whether the variation in the colour and number 

 of bands of the shells of such sj)ecies as Helix 

 nemoralis and H. hortensis deserves all the attention 

 it is receiving, I will not venture to say. I think, 

 however, that these variations may be regarded as 

 at least worthy of some study by those who have 

 time to devote to it. The local distribution of some 

 of these colour-varieties is rather interesting. By 

 the side of the branch line connecting the quarries 

 in Shielhill Glen with the Wemyss Bay Railway, I 



