Lillian is the third child for the star of In Plain Sight
This U.S. marshal now has her own posse.
Mary McCormack, who hunts down witnesses on In Plain Sight, delivered her third daughter, Lillian, on Saturday morning, Sept. 10, her rep confirms to PEOPLE.
Lillian weighed in at 6 lbs., 15 oz. and is 20 inches long.
The actress, 42, and husband Michael Morris s new arrival joins big sisters Rose, 4, and Margaret, 7.