LAND AND FRESH- WATER MOLLUSC A FROM TARBERT. 129 



IX. 



REMARKS ON SOME LAND AND FRESH- WA TER 

 MOLLUSC A FROM TARBERT, LOCH FYNE. 



BY THOMAS SCOTT. 



[Read 26th April, 1887.] 



So far as could be ascertained during the time at 

 my disposal, the specimens now exhibited are fairly 

 representative of the Land and Fresh-water Mollusca 

 occurring about Tarbert, Loch Fyne. When compared 

 as a whole with those from other districts in 

 Clydesdale, they present some rather interesting 

 points of difference. It will be noticed that aquatic 

 species are but poorly represented — one or two 

 Pisidia, the same number of Limncece, and an Ancylus, 

 exhausting the list. Of the Planorbi, which have a 

 wide distribution, no fewer than five species are 

 found within a short distance of Rothesay, but none 

 were observed at Tarbert. This scarcity of fresh- 

 water forms is probably due to the rugged and 

 hilly nature of the district, which does not admit of 

 conditions very favourable to the propagation of 

 these molluscs. The land molluscs, on the other 

 hand, are well represented both as regards genera 

 and species ; and among them, especially in the larger 

 Helicidce, a rather unusual number of varieties have 

 been observed. 



Helix aspersa, Mull., showed a good deal of variation 

 in the number and arrangement of the bands ; and 

 three distinct varieties of form were observed. The 

 following are some of the band variations : 



(12345) — unicoloured ; 



(12)(345), 12(34)5 — bands partly united and 



partly free ; 

 12345— all the bands distinct. 



