370 Proceedings of Societies. 



It is worthy of remark, that there are shells very abundant on the 

 roast, and which, from their littoral character, must have been quite as 

 much exposed to the intense cold as either Mactra stultorwm or Solen 

 tiliqua, of which I did not find a single dead specimen on the beach. 

 Tellina solidula is one of these species, and Mactra solida, with its sub- 

 species or variety Mactra truncata, another; and these the frost seems 

 not to have in the least affected. Of the various littoral univalves, too, 

 including the periwinkles, purpura, and trochiclse, only one species — 

 Natica monilifera — seems to have suffered. Now, Tellina solidula is in 

 some localities, — as at Castleton King-Edward, — one of the most numer- 

 ous and best developed of the boreal shells ; Mactra solida is also a boreal 

 species, with the common periwinkle Littorina littorea, the common 

 purpura P. lapillus, and the dog-periwinkle Trochus cinerarius. Again, 

 on the other hand, of the destroyed shells, I have not yet found any trace 

 of Tellina fibula or Donax anatinus in the old glacial deposits, such as 

 the boulder clay, or Gamrie gravels and sands, nor yet of Mactra stul- 

 torum or Solen siliqua, though the former is said to be a shell of the 

 Mammiferous Crag, and the latter of the Clyde beds. And though a 

 large natica occurs in both the Caithness and Gamrie deposits, that very 

 considerably resembles Natica monilifera, it fails to exhibit the charac- 

 teristic flexuous streaks, and in general form seems at least as much akin 

 to a sub-arctic species as to the one recently killed by the frost. And 

 there can be, I think, no doubt that the boulder clay Tellina, T. proxima, 

 is altogether a different species, notwithstanding its points of similarity 

 in the more dwarfish individuals, from Tellina, tenuis. None of the 

 molluscs killed in any considerable abundance by the present intense 

 frost seem to be truly boreal species ; and their destruction by the refri- 

 gerating agent, which has strewed them by millions along the beach, 

 seems not only strikingly illustrative, as I have said, of one of the modes 

 in which species may be destroyed, but also of a curious passage in the 

 later geologic history of Northern Europe. It is an ascertained fact, that 

 shells were living in the British area during the times of the Red Crag, 

 of the same species with those recently killed by the frost ; Mactra stul- 

 torum is one of these, and Natica monilifera another ; and they now 

 live in the neighbouring frith ; but J at least have failed, after sedulous 

 exploration, to detect them in the intermediate period of boreal shells, 

 ice-grooved surfaces, and the boulder clay, — a period during which some 

 of their hardier cogeners were very abundant. And the catastrophe 

 which has just destroyed them in such numbers shows in part how this 

 passage in our geologic history may have taken place. 



2. On the Silurian and Old Red Floras of Scotland. By Hugh 

 Miller, Esq. — Mr Miller illustrated his paper by the exhibition of a 

 most interesting collection of the fossil remains of these little-known 

 plants. 



3. On the Homology of the Vertebrate Skeleton, and its representative 

 Eso-Sheleton of the Invertebrate Classes, with the application to Zoology, 

 Palaeontology, and Geology. By Professor M'Donald. — The Professor 

 exhibited a numerous collection of osteological preparations and diagrams 

 in illustration of his peculiar views. 



