NATURAL HISTORY SOCIETY OF GLASGOW. 41 



caused by the conditions of the sea bottom on which it lived. 

 Mr Davidson states, that at the time when he commenced his 

 investigations amongst the British Carboniferous Sjnrifera, there 

 were about one hundred and seventeen described species. After 

 a long and searching investigation, he came to the conchision that 

 eiglity-six of these so-called species were mere synonyms and 

 varieties, and out of the thirty-one species admitted to his lists, 

 only some twenty-three have been satisfactorily determined. All 

 this variation, therefore, favours the view that many of the closely- 

 allied forms once ranked as species, are only varieties of one 

 original type. 



One point in connection with the distribution of Sinrifera 

 trigonaUs and its varieties in our strata I wish to refer to before I 

 have done, and that is its disappearance throughout a consider- 

 able thickness of strata, represented by the fresh-water beds of our 

 middle coals and ironstones of the Possil and Govan group. The 

 absence of decidedly marine remains from this group of strata, 

 points to physical conditions that once more shut out the sea from 

 the space occupied by their area, and during which the strata 

 accumulated w^ere such as had either grown upon land, or had 

 been deposited in lake bottoms of fresh water origin. Witli the 

 return of the sea, during the upper limestone period, returned also 

 Sjmifera trigonaUs, and some of its varieties, as well as many other 

 of the older forms of Carboniferous marine life. These maintained 

 for a period a sort of shifting existence, until they finally 

 disappeared, by the shutting out of the sea during nearly the 

 whole time of the deposition of the upper Carboniferous coal 

 measures. Evidences of these physical changes are derived from 

 the study of the groups of fossils found in the various strata, these 

 affording the only true key to the history and conditions of the 

 fossiliferous sedimentary deposits of every geological period. 



II. — On some Plants rare in the West of Scotland, ohserved during 

 last Summer. By Mr Jaimes Eamsay, Vice-President. 

 Mr Eamsay stated that on 3d July, 1875, along with Prof. A. 

 Dickson, he had visited the island of Cumbrae, and while passing 

 along the margin of a field of oats, just coming into ear, they 

 discovered among the corn a great many plants of the Night- 

 flowering Catch-fly (Silene noctiflora), an annual species, confined 

 in Scotland entirely to the eastern counties. This was the only 



