382 TABLE OF DISTRIBUTION. 



the same is true of the other species recorded from there. Off the mouths of 

 large rivers, too, like the Amazon, Siphonophores are rare or absent (Chiui, '97b, 

 p. 101). 



TABLE OF DISTRIBUTION. 



In the ensuing table, the well-authenticated occurrences of all valid, and 

 several doubtful species are given, so far as I have been able to find them. 

 Unplaced Eudoxids are omitted. 



The words "tropical," "temperate," etc, are vague, and do not always carry 

 the same meaning. I have therefore divided the north Atlantic into four zones; 

 1, warm regions limited by the isotherm of 68°; 2, temperate, 68°-55°; 3, boreal, 

 55°-45°; and 4, Arctic, below 45°. These limits are all for the warmest month 

 of the year, because the great majority of Siphonophores are warm-water forms, 

 and often occur in summer far to the north of their usual range, particularly 

 in the region of the Gulf Stream. The precise temperature limits have been 

 chosen because they fit in best with the distribution of the group. A fifth 

 region is the Mediterranean. 



The curves on the small chart are taken from Krummel, the Deutsche 

 Seewarte atlas, the "Ingolf" Expedition, Nansen (North Polar Expedition), 

 and from the data collected by the "Conseil International." 



The Indian and Pacific oceans are treated as a whole, because our knowledge 

 of their Siphonophore fauna is practically limited to the tropical and subtropical 

 regions. And the south Atlantic is omitted for the obvious reason that it is 

 practically mare incognitum in this connection. 



A complete list of the records of Siphonophores in northern waters up to 

 1902 has been compiled by Romer (:02). 



The sign X indicates that the species is known; — ■ that it is represented by 

 an ally so close that the two may finally prove to be identical. X indicates 

 that the species is known from intermediate or closing net hauls only. Species 

 preceded by ? are problematical. O signifies that the genus is known, but that 

 its specific representative is doubtful. 



