Sentence:  Laurence M . Klauber put length at maturity at two thirds the ultimate <WSD>length</WSD> for some rattlesnakes , and Charles C . Carpenter 's data on Michigan garter and ribbon snakes ( Thamnophis ) show that the smallest gravid females are more than half as long as the biggest adults . 
Meaning of the word marked with <WSD> tags:  the linear extent in space from one end to the other; the longest dimension of something that is fixed in place