Sales of Motorola Inc.'s cellphones crumbled in the important holiday season, dropping more than 50% from the year-ago quarter and prompting the company Wednesday to announce it was eliminating another 4,000 jobs.

Motorola is scrambling to stem losses in its flagship mobile devices division, which sold 19 million phones in the fourth quarter, down from 25.4 million in the third quarter and 40.9 million in the fourth quarter of 2007.

The...