196 U.S. NATIONAL MUSEUM BULLETIN 291 



are all relatively shallow-living forms that have 70% to 85% of their 

 numbers in less than 1000 m; only 13% of all B. dbyssicola captured 

 occur in less than 1000 m. Taken together the three common shallower 

 living species outnumber B. dbyssicola by 13%. Assuming that the 

 trawling gear is mutually selective, the implication is that the shallow 

 end of the vertical range of B. dbyssicola overlaps with the deeper parts 

 of the ranges of Crystallotheuthis glacialis, Brachioteuthis picta, and 

 Gonatus antarcticus^ and that B. ahyssicola replaces these three species 

 in the greater depths. 



Approximately 15 additional species of squid of the suborder Oegop- 

 sida were collected in Antarctic waters through Cruise 15 and their 

 numbers total less than 250 specimens. The most common of these, 

 Alluroteuthis antarcticus Odhner, 1923, is represented by 69 specimens. 

 Deeper dwelling forms, e.g., species of Mastigoteuthis, Chiroteuthis, 

 and Histioteuthis, are represented by fewer than two dozen specimens 

 each. 



Therefore, the dominance of Bathyteuthis abyssicola in the total 

 known Antarctic cephalopod fauna, as well as among the bathypelagic 

 inhabitants, is undisputed. It is a striking example of a species that 

 occurs in small to moderate numbers over a broad geographical range 

 but is so successfully adapted to a particular environment that it is 

 the dominant species. 



