Sentence:  The following story was the first fruit of my New York life when I began to live it after my quarter of a century in Cambridge and Boston, ending in 1889; and I used my own transition to the commercial metropolis in framing the experience which was wholly that of my <WSD>supposititious</WSD> literary adventurer. 
Meaning of the word marked with <WSD> tags:  Imaginary; fictitious, pretended to exist.