E. M. Kindle — Bottom Control of Marine Faunas. 453 



Station 2 with a soft blackish mud bottom furnished 10 

 species of pelecypods and gasteropods. Only 2 of these or 21 

 per cent are common to the fauna of the stations with hard or 

 rocky bottom. One of these two is the Littorina litorea, 

 a species which has nearly universal distribution in the inter- 

 tidal and very shallow water zone. Station 3 with a muddy, 

 sandy bottom yielded 24 species. Only 5 of these 24, or 20 

 per cent of the fauna, are found at stations 6 and 10, which are 

 typical hard bottom stations. The composition of the fauna 

 of station 3 compared with that of station 2, however, reveals 

 a very close relationship between the two. Nine of the 10 

 species or 90 per cent of station 2 are present in station 3. 

 Thus we find that the likeness and differences between the 

 faunas at the different stations are directly correlated with the 

 resemblance or contrast shown by the types of bottom at these 

 stations. Summing up these observations we find that in the 

 case of two stations with hard bottom 72 per cent of the species 

 of each station are common to the fauna of the other. A soft 

 mud bottom shows a fauna with only 21 per cent of its species 

 common to the fauna of the hard bottom station. This soft 

 mud fauna compared with the fauna of a rather closely allied 

 type of bottom composed of muddy sand shows 90 per cent of 

 its species common to the fauna of the latter type of bottom. 

 In other words the faunules from different stations in the same 

 general region resemble each other in composition in approxi- 

 mately the same degree as do the bottom materials on which 

 they live. 



In the preceding comparison of faunules from different 

 types of bottom only the gasteropods and pelecypods have been 

 considered. If, however, we include in the comparison the 

 total fauna as represented by both living and dead forms taken 

 from each station the contrast in the case of unlike bottoms is 

 even more striking than when only the two groups above men- 

 tioned are made the basis of the investigation. The total 

 fauna collected at station 2, which has a soft black mud bottom, 

 includes 14 species while station 10 with a hard bottom yielded 

 26 species including living and dead forms. Only three species 

 or 7 per cent of the total fauna of the two stations are com- 

 mon to both stations. Since in this comparison both living 

 and dead shells are included, it disposes of the contention of 

 some geologists, that while the assemblage of living forms may 

 be conditioned by the kind of bottom the mixing of the dead 

 shells by current action destroys in the fossil fauna any dis- 

 tinctions between facies representing distinct types of bottom. 

 It is true that in certain areas a limited amount of this post- 

 mortem shifting of faunules may occur. But the dredge in- 

 dicates that its relative importance in moMfying the character 



