Spouse's SS retirement benefits

A spouse who has not worked or who has low earnings can be entitled to as much as one-half of the retired worker’s full benefit. If you are eligible for both your own retirement benefits and for benefits as a spouse, Social Security will always pay your own benefits first. If your benefits as a spouse are higher than your retirement benefits, you will get a combination of benefits equaling the higher spouse benefit.

If you have reached your full retirement age, and are eligible for a spouse's or ex-spouse's benefit and your own retirement benefit, you may choose to receive only spouse's benefits and continue accruing delayed retirement credits on your own Social Security record. You may then file for benefits at a later date and receive a higher monthly benefit based on the effect of delayed retirement credits.

See here for details :
http://www.socialsecurity.gov/pubs/10035.html