Sentence:  Midway in the mound is a platform of large bricks stamped with the names of Sargon of Akkad and his son Naram-Sin (3800 B.C.); as the débris above them is 34 ft. thick, the topmost stratum being not later than the <WSD>Parthian</WSD> era (H. V. Hilprecht, The Babylonian Expedition, i. 2, p. 23), it is calculated that the débris underneath the pavement, 30 ft. thick, must represent a period of about 3000 years, more especially as older constructions had to be levelled before the pavement was laid. 
Meaning of the word marked with <WSD> tags:  Relating to Parthia or Parthians.