Sentence:  ...left mandible with broad, flat lacinia mobilis set in <WSD>seatment</WSD> so surface flush with extremes of incisor, right incisor also with mostly unserrate straight margin as in left, right lacinia mobilis spiniform, each mandible with two spines, no molars, no palps; 
Meaning of the word marked with <WSD> tags:  The location or facilities provided for someone or something to be seated in.