NATURAL HISTORY SOCIETY OF GLASGOW. 279 



may at times fall into our hands, and there can be little doubt 

 that even with recent forms individuals may have frequently 

 been raised to tlie rank of species, which were nothing more than 

 functionally imperfect animals. This must be all the more likely 

 to happen with fossils where the diagnosis has often to be made 

 from a crushed individual, or a fragmentary portion of a shell. If 

 a body whorl was met with in some of our Carboniferous shales 

 which, under similar circumstances to one of these shells before 

 us, was devoid of its characteristic striae, and enlarged beyond 

 its normal size, it is almost certain that it would be referred to a 

 different species, or described as new. 



A discussion followed the reading of this paper regarding the 

 functions of the mantle in molluscs, in which the Chairman, Mr 

 D. 0. Glen, F.G.S., and others took part. 



December 18th, 1877. 



Mr James Barclay Murdoch, Vice-President, in the chair. 

 Messrs. AYilliam Horn, Edinburgh, Eobert Bennett Browne, and 

 John M. Martin, were elected ordinary members. 



SPECIMENS exhibited. 



Mr David Eobertson, jun., exhibited a pair of Black-throated 

 Divers, Colymhus ardiciis, Linn., got on a small islet in Loch Awe 

 in May, 1876. Mr Eobertson remarked that these birds were 

 in full summer plumage, a condition in which they are seldom 

 found, especially so far south as Loch Awe. The sj)ecies 

 frequents principally the lakes of Norway and Sweden, and 

 Hudson's Bay, North America ; and in Scotland is chiefly found 

 in the north, where it breeds in the lochs of Eoss and Sutherland, 

 and in the Hebrides. In 1850 it was obtained in several parts 

 of England, but so far as is known, in all cases the specimens 

 were in winter plumage. In Ireland it is very rare, having only 

 occurred two or three times. Mr Harvie-Brown, who has often 

 met with this bird in the northern counties of Scotland, made 

 some remarks on the specimens. 



Mr Arthur Pratt exhibited a fine series of the heads and stems 

 of various species of Crinoids, from the limestone strata at 

 Invertiel, near Kirkcaldy, and other districts in Fifeshire, amongst 



