MIDLANTIC <MIDL.O> TO ACQUIRE COUNTY BANCORP Midlantic Corp said it agreed to acquire County Bancorp for about 23 mln dlrs in an agreement calling for County Trust Co, a County Bancorp subsidiary, to merge into Midlantic National Bank/North. Midlantic said it will pay 83.73 dlrs a share in cash, or 2.36 times County Bancorp's March 31 book value, for each of County's about 276,0000 shares outstanding. It said it received an option from three principal shareholders for 40 pct of County's outstanding. The acquisition is expected in the third quarter of 1987 and is subject to regulatory and shareholder approvals.