Proceedings of the British Association. 115 



Section D. — Zoology and Botany. — Thursday. 



Dr. Pritchard read a paper on 'The Extinction of the Human Races.' 

 He expressed his regret that so little attention was given to Ethnogra- 

 phy, or the natural history of the human race, while the opportunities 

 for observation are every day passing away ; and concluded by an appeal 

 in favour of the Aborigines' Protection Society. The paper gave rise to 

 a long and desultory conversation, in which Dr. Hodgkin, Mr. Wilde, 

 Mr. Watson, Mr. Hall, Dr. Daubeny, Dr. Wilson (of America), Mr. 

 Thompson, and others, took part. 



A Report on the Disbribution of the Pulmoniferous Mollusca in Bri- 

 tain, and the Causes influencing it; drawn up at the request of the 

 Association, by Mr. E. Forbes. — The object of this inquiry was to ascer. 

 tain the geographical and geological distribution of pulmoniferous mol- 

 lusca in the British isles. The subject was considered under three heads : 

 first, a view of the various influences which affect their distribution ; se- 

 cond, a detailed view of the distribution of the indigenous species in the 

 various provinces of Britain ; and third, the relations of that division of 

 the native Fauna to the Fauna of Europe, and the distribution generally 

 of the more remarkable species. Under the first head, after enumerating 

 the various species of pulmoniferous mollusca inhabiting Britain, Mr. 

 Forbes proceeded to review the causes influencing their distribution, 

 dividing such causes into primary and secondary. Under the head of 

 primary causes, he considered the two influences of climate and soil. 

 The influence of climate in Britain is indicated by the reduced number 

 of species found in the more northern or colder districts, as compared 

 with the number inhabiting the provinces of the south and centre. It 

 is also indicated by the disappearance of species which inhabit soils in- 

 differently, as we advance northwards, and by the presence of species in 

 certain situations in southern and warm districts, which usually avoid, 

 or are sparingly found in such localities. It is further shown by the 

 tendency of individuals to multiply in temperate situations, and by the 

 superior beauty of colouring displayed by species inhabiting warm dis- 

 tricts. The author then pointed out, that there existed in many places 

 a stronger influence than climate, and showed that this influence was in 

 its nature geological. He showed that various kinds of rocks influence 

 the distribution of mollusca ; that calcareous rocks are especially fa- 

 vourable to their distribution ; and that all rocks containing much lime 

 tend to increase both the number of species and of individuals living on 

 them. Certain species are confined altogether to certain rocks, others 

 to a class of rocks ; and instances of the occurrence. of such phenomena 

 in Britain were enumerated. Some rocks influence the distribution ne- 

 gatively, diminishing the number both of species and individuals. The 

 order of influence of rocks on species in Britain, is as follows, commen- 

 cing with the most influential : — 



1. Cretaceous and oolitic. 



2. Carboniferous rocks and trap. 



