174 PROCEEDINGS OF THE 



refuse into it. I fear that before this time all that lived in that 

 once pure water may be poisoned by, or buried under the debris 

 of, the streets. 



I find that lochs and ponds in ihe neighbourhood of towns are 

 in general more rich in mollusca, ostracoda, and other microzoa, 

 than those in more secluded localities, where water-fowl, which 

 feed greedily on molluscs and other aquatic animals, congregate 

 in greater abundance. 



However, this suburban immunity of aquatic animals is only 

 partial, for what they gain in one way they may lose in another. 

 Where relieved from the presence of water-fowl, they may be 

 attacked by the deleterious products of sewage, but even when so 

 exposed, it is astonishing how some animals survive and thrive 

 abundantly, while others of the same class succumb. This explains 

 in a great measure why some species often prevail and are differ- 

 ently associated in different localities. At the Glasgow terminus 

 of the Paisley Canal in Eglinton Street, where the water is 

 strongly charged with the sewage from neighbouring factories, 

 the little ostracod Cypris compressa, swarms in the most filthy 

 mud at the bottom, and is plump and sleek as if quite at home, 

 while scarcely any of its usual associates are to be found. The 

 same may be said of the estuary of the Clyde. Over the muddy 

 flats near Langbank,* the small invertebrate fauna is unusually 

 sparse, with the exception of one or two forms, which are in 

 great abundance. 



Of the third shell I have to bring before you. Helix villosa, four 

 living specimens were taken on the flat ground or moors near 

 Cardiff, by Mrs Robertson. 



As I was not able to refer them to any British species, they 

 were submitted to Mr Jeffreys, who pronounced them to be 

 Helix villosa (Draparnaud), and has recorded the species in Annals 

 and Mag. Nat. Hist., Jan. 1877, as an addition to the British 

 mollusca. H. villosa inhabits Germany, France, and Switzerland, 

 and it often occurs at a considerable height above the level of the 

 sea. Mr Jeffreys refers to //. alpcstris, a British variety of 

 H. arhustorum, as having similar habits. It is met with on the 

 Swiss Alps, in the region of perpetual snow, as well as in the 



* Transactions of the Geol. Soc. of Glasgow, Vol. V., Part I,, p. 112. 



