460 E. M. Kindle — Bottom Control of Marine Faunas. 



Acadian fauna of the Bay of Fundy is pretty well known. 

 The boreal fauna of X. Labrador is comparatively little known 

 but a representative collection compared with the fauna of the 

 Bay of Fnndy should give an approximate idea of the influence 

 of latitude in differentiating the two faunas. I have selected 

 for comparison with the Bay of Fundy fauna a collection from 

 Ungava Bay made by Turner and determined by Dr. Dall.* 

 The pelecypods and gasteropods of this collection include 17 

 species. Comparison of these with the entire known fauna 

 recorded for the corresponding groups from the Bay of Fundy 

 shows that onty 53 per cent of the Ungava Bay fauna is com- 

 mon to the fauna of the Bay of Fundy. The entire recorded 

 fauna of the Bay of Fundy probably represents every type of bot- 

 tom that would be met with in Ungava Bay. Hence this factor 

 would be negligible in this comparison and the difference in 

 composition presumably represents the influence of latitude 

 and the attendant differences in water temperature. In other 

 words the difference in latitude of the two regions, which is 

 about IS degrees, results in a fauna at the northern locality 

 47 per cent of whose species are unknown in the Bay of Fundy. 

 If the faunal difference due to a latitude difference between 

 Ungava Bay and the Bay of Fundy is compared with the 

 faunal differences due to character of bottom which have 

 already been shown from the tables for the west coast of Nova 

 Scotia, it is seen that the latter are much more pronounced. 

 The single example taken of the Labrador fauna shows a dif- 

 ference in faunal composition of 47 per cent resulting from a 

 latitude difference of 18°. The tables given in this paper 

 show that 80 per cent of a black mud fauna fails to appear on 

 a gravel and rock bottom. In the case of a hard bottom fauna 

 100 per cent sometimes fail to pass over to a sand bottom 

 habitat. The conclusion is therefore reached that differences 

 in the physical character of the bottom are often even more 

 effective than great differences in latitude in determining the 

 composition of a fauna. 



Bearing on Geology. 



The geological significance of the observations recorded in 

 this paper may be more clearly indicated if for the sake of 

 illustration subsidence is assumed to occur which would lower 

 the mouth of the Avon River in western Nova Scotia 100 

 feet below its present level. This would reduce the present 

 strong currents so that the channel on either side the long 

 barren sand bar, which now splits the lower end of the 

 estuary, would fill with sandy mud to the top of the bar and 

 eventually bury it under 30' or more of sediment of a type 

 *Proe. U. S. Nat. Museiira, vol. ix, pp. 202-208, 1886. 



