Mars de Saham—Portum Pusillum

The first appears to be Soham, in Cambridgeshire; described in *Liber Eliensis* as "terra de Saham, quæ est ad stagnum juxta Ely." Does "mare" stand for "stagnum," "palus," "mariscus," or our English "mere?" Can Portum Pusillum be Littleport, in the same country?