NO. 1704. A COLLECTION OF SHELLS FROM PERU—DALL. 191 



The notion that the niournful colors of so many of the species 

 might be correlated with the huge beds of kelp characteristic of 

 these shores seems to be negatived by the fact that in California 

 similar kelp beds afford a shelter to some of the most brightly colored 

 Trochidse, etc., and that, as I am informed by Mr. Coker, red and 

 green seaweeds are abundant on the rocks below low-water mark, on 

 a. large part of the coast of Peru, and presumably also of Chile. 

 This and a number of other problems await the investigations of the 

 future. 



Lastly, a survey of the characteristic groups of which the fauna 

 is largely matle up leads to the conclusion that the fauna is cliiefly 

 of southern origin. In spite of the fact that many species are com- 

 mon to the Panamic fauna and a relatively small number to the 

 Magellanic fauna, the more conspicuous types, like the blackish 

 species of Tegula, have a Magellanic rather than a tropical character. 

 This particular group has extended its range to Alaska on the north 

 and Japan on the northwest, but its metropolis is in southern Chile. 

 The type represented by the various species of Thais and Acanthina 

 has traveled the same road, and so has the Protothaca group of 

 Venerid^. 



If we may accept as the original metropolis of a special type of 

 mollusks that region where it is developed in the greatest number 

 and variety of species, and perhaps also with the most extreme 

 limits of size and ornamentation, we shall have for example Buccinum 

 and Clirysodomus focused in the boreal Pacific region, certain types 

 of Thais and Acanthina in the region of southern Chile. 



Cook has called attention to the relation between Thais lapillus 

 and the Oregonian T. lamellosa, and other species in the Tropics of 

 the Panamic and Antillean region; but, viewed from an Eastern 

 Pacific standpoint, the relatively few Atlantic forms may easily have 

 originated in the Pacific, where their existing representatives show 

 a much more luxuriant development. 



There is only one Thais of the Nucella type in the North Atlantic, 

 but the North Pacific has five or six. It is very remarkable that in 

 the Peruvian Province we have not a single distinctively old world 

 type of mollusk. Those which seem to be such are really cosmo- 

 politan types, more familiar to us from old world localities, perhaps, 

 but not necessarily of okl world origin. 



