Undated (AP) _ The Navigators Group Inc. said Wednesday it has agreed to acquire the Somerset companies, eight affiliated firms that provide insurance underwriting management services to Navigators Insurance Co. and other insurance writers.

Under the agreement, Somerset stockholders will receive 2,875,000 shares of Navigators common stock, worth about $103.5 million at current trading levels.

The deal, expected to close in the first quarter of 1994, calls for a wholly owned subsidiary of Navigators to merge with each of the Somerset companies.

Navigators, through its wholly owned subsidiaries Navigators Insurance and NIC Insurance Co., specializes in marine, aviation and property insurance, and certain lines of specialty reinsurance.