Over 150,000 line-kilometers of low-level (152 m) aeromagnetic data were recorded in the western Arctic Basin by the U.S. Navy during four field seasons (1975--1978); data from the first 2 years were presented by Vogt et al (1979a), while the data from the last two years are described in this paper. These data (1977--1978) cover a swath from the north slope of Alaska to the north geographic pole. Flight lines were spaced between 10 and 24 km. The east-west oriented aeromagnetic profiles across the Canada Basin and the Beaufort Sea suggest that Alaska was moving away from the Queen Elizabeth Islands of the Canadian Arctic from 153 m.y. B.P. (anomaly M-25 time) to 127 m.y. B.P. (M-12), at an opening rate of 2.6 cm/yr. An extinct spreading center is defined by a positive free-air gravity anomaly, with the relic spreading axis generally paralleling the 150˚ W meridian. We are unable to recognize a coherent pattern of lineated anomalies over the Alpha Ridge: therefore its origin remains uncertain. A series of seafloor spreading type anomalies have been tentatively identified in the Fletcher (Makarov) Basin. Spreading began in the Upper Cretaceous (anomaly 34; 80 m.y.B.P.) and continued until mid-Eocene (anomaly 21; 53 m.y. B. P.); total opening rate was about 1.7 cm/ry. During the opening of the Fletcher Basin, rifting began in Baffin Bay and the Norwegian and Labrador seas and the Eurasian Basin. Our results suggest a tectonic coupling between these areas at this time, with the Nares Strait acting as a transform fault and serving as a connector with the Baffin Bay/Labrador Sea speading centers.