BIGELOW: COAST WATER EXPLORATION OF 1913. 



299 



The most important feature of the collection, from the geographic 

 standpoint, is the presence of a very characteristic tropical fauna, i. e., 

 Sagitta enflata, S. hexaptera, S. bipunctata, small S. serratodentata, 

 and Ptcrosagitta draco in the coast water south of Delaware Bay and 

 in the inner edge of the Gulf Stream. This is just what was to be 

 expected from hydrography, and agrees with the tropical aspect of the 

 plankton as a whole in those regions. 



Elsewhere in the Grampus collecting ground the chaetognath fauna 

 is typically boreal, characterized by the presence of Sagitta elegans 

 in abundance, and of large specimens of S. serratodentata. Though 

 Sagittae were taken at nearly all our Stations, it was only at 

 eight (10057, 10059, 10060, 10061, 10070, 10103, 10105) that they 

 were an important constituent of the plankton, quantitatively 

 speaking. 



Sagitta elegans was the prevalent Sagitta in the Gulf of Maine, 

 where it was found at all Stations, three times in swarms (10057, 10103 

 10105). It likewise swarmed on George's Bank early in July (Station 

 10059) ; and was the most abundant species over the continental shelf 

 east of Long Island. But it was rare in the coast water further 

 west and south, and lacking outside the continental slope, as well as 

 over the shelf south of Delaware Bay. And this agrees with its 

 boreal habitat on the other side of the Atlantic. It was usually most 

 abundant at about twenty fathoms depth; being numerous on the 

 surface on one occasion only. 



Sagitta serratodentata was likewise taken in the Gulf of Maine; but 

 at eight stations only, and always in small numbers. And it was less 

 numerous than elegans over the shelf south of Marthas Vineyard. 

 But it was the prevalent Sagitta in the shallow waters south of New 



