280 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 7, 



Of the above shells the Turritella and Cyprina are probably the 

 most common. Astarte, Natica, Tellina, Saxicava, and Mya are also 

 pretty frequent, and so likewise are Dentalium entalis, Ledapernula, 

 Gardium echinatum, and Mangelia turricula. The scale of frequency, 

 however, differs in different localities. Some of the species have 

 been determined from single fragments, as, for example, Venus ovata 

 and Trochus zizyphinus. 



Patella vulgata is a shell I have never myself found in any of our 

 Scotch glacial beds, but Mr.' Peach informs me he got one pretty 

 perfect specimen, besides two or three fragments. Mr. Dick also 

 told me he had found it. In regard to some of the other species 

 Mr. Peach has supplied me with the following information : — " JPecten 

 maccimus and opercularis, in fragments, occur frequently. Cardium 

 Norvegicum, two or three hinge-pieces. Fusus antiquus, two pillar- 

 lips. Ostrea edulis, one pretty large shell and several fragments " ; 

 and he says there can be no doubt whatever that these occur in the 

 very same deposits as the more Arctic forms. 



Table II. — Showing the Geographical relations of groups of Mollusca 

 whose Shells occur in some of the Scottish Glacial beds. 





Errol. 



Elie. 



\ King- ) 

 'I Edward. ) 



Paisley. 



Kilehattan. 







( Fort 

 i William. 



Total number^ 













of species at I 



13 



14 



27 



26 



16 



25 



75 



47 



each locality J 



















Southern, per 1 



cent. 

 British, „ .. 



8 



14 



44 



38 



50 



52 



61 



55 



38 



43 



59 



61 



69 



72 



80 



85 



Northern, „ . . 



62 



57 



93 



100 



100 



96 



88 



96 



Arctic, „ . . 



100 



100 



100 



100 



100 



100 



84 



89 



N.E. Ame- \ 

 rican, „ J 



100 



100 



89 



85 



87 



88 



55 



70 



Some interesting information may be gathered from the foregoing- 

 Table. 



The Errol and Elie groups, it will be seen, are intensely Arctic ; 

 the shells are just such as we might find in the sea of Spitzbergen at 

 the present day, many of the species not ranging south of the Arctic 

 circle. In them the proportion of British species is less than 50 per 

 cent., while that of the Southern has dwindled down to a very small 

 fraction. These two groups I take to represent an early stage of the 

 glacial-marine beds when the rigour of the climate was at its height. 



The groups from King-Edward, Paisley, Kilehattan, and Gamrie 

 probably belong to a somewhat later stage, for although the general 

 character is still Arctic, yet it is less strictly so than in the two pre- 

 ceding. The proportion of Southern forms is far greater, and the 

 British exceed 50 per cent. 



The Eort William group is probably the latest of all; it is no 

 longer Arctic but Northern, and the British species exceed 80 per 

 cent. 



