mersc
This might be just a supplemental entry adding to an entry in the Main Volume.
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
mersc
AddHíredes seota tó présta túne, and se mersc se tó ðam ilcan lande belimpð . . . isti sunt termini. . . marisci; in oriente híredes mersc tó présta túne, C. D. ii. 102, 29-33. Hí wendon ofer Temese . . . and swá wið Caningan mærsces (mersces, v. l. ), Chr. 1010; P. 141, 6. Segor stód on midwege betweox ðǽm muntum and ðǽm merscum ðe Sodoma on wæs.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.