REMARKS UPON THE DISTRIBUTION OF ANIMALS AND PLANTS. 567 



of the terraces are all that can be relied upon to suggest so great a 

 submergence. 



From molluscan remains it is proved that the Hudson and Champlain 

 valleys were covered by salt water in the period now under consideration. 

 The proof of submergence, from the occurrence of maritime plants, is 

 very meagre, only four species appearing on the list. It is possible that 

 future researches may add to the list, though not in large numbers, after 

 the researches of Oakes, Tuckerman, Torrey, Zaclock Thompson, and 

 Peck. It may likewise be observed that the lower St. Lawrence fur- 

 nishes fewer species than the borders of the great lakes. These defi- 

 ciencies were so patent, that Mr. Peck, in his reply to my inquiries, 

 regarded "the connection between the maritime plants of the region of 

 the great lakes with the Atlantic ocean, by intermediate stations, as not 

 well shown." Is it not possible that these breaks in the connection are 

 proofs of the correctness of our theory? If the continued existence of 

 these plants about the lakes is due to the presence of large bodies of 

 water, even in the absence of salt, then we should not expect to find 

 them remaining along the narrow Champlain, nor the still narrower 

 Hudson river, nor, to a large extent, the St. Lawrence. The conditions 

 are not favorable to their preservation. Furthermore, if the species were 

 equally distributed from the ocean into the interior, or especially if they 

 became fewer in number the farther they penetrated the continent, it 

 might be said that they had migrated, since the Champlain period, even 

 to Minnesota. Hence what might appear destructive of our theory is 

 in reality a strong argument in its favor. These considerations were 

 forcibly set forth in a private communication from Dr. Ward. 



It might be said by some that the plants in the salt regions of western 

 New York existed there naturally on account of the presence of saline 

 matters in the soil. This circumstance will not, however, explain their 

 origin. During the glacial period all life was destroyed by the intense 

 cold. Hence the salt-loving plants disappeared. With the return of 

 the warm temperature, the plants could not return by an overland emi- 

 gration. They could return only by a gradual migration along a shore 

 line, whether salt or fresh, unless it be supposed plants were created for 

 this special locality. The latter supposition is untenable, since a special 

 creation is not required to explain the distribution of the other plants in 



