Sentence:  In contrast , Ditmars recorded the average length of seventy-two young of a 19 - <WSD>foot</WSD> female as 38 inches , and four young were born in London at a length of 35 or 36 inches and a weight of from 14 to 16 ounces . 
Meaning of the word marked with <WSD> tags:  a linear unit of length equal to 12 inches or a third of a yard