Mary Bjornson, age 11, of Hattiesburg, Miss., for her question:

WHAT IS A SEA COW?

A sea cow is a term that applies to an extinct animal more properly called Steller's sea cow. Sometimes the term is improperly applied to the dugong and manatee, which belong to an order or group of sea mammals called Sirenia.

The Stellar's sea cow was discovered in 1741 near the Commander Islands in the Bering Sea. The total population then probably numbered between 1,000 and 2,000.

Sailors killed the animals for food and by 1768 the Steller's sea cow was no more. It was indeed extinct.

The Steller's sea cow lived in shallow water near shore. It fed on seaweed. It was the largest sirenian and the only one adapted to cold water.

The Steller's sea cow was a gigantic mammal. It grew to be about 23 feet long and weighed about 9,000 pounds.