Jas.

Jas. is a clerk's shorthand for the given name James. Writers shortened common first names to save time and ink, usually by keeping the first letters and the last one or two, often with the final letters raised above the line.

Do not confuse it with Jos. (Joseph) or Jno. (John); the three look alike in faded handwriting, so compare the letters with other words written by the same clerk. In the census it is almost always James.