Searching through lists with Scheme (DrRacket)

So here's my code:

(define *graph* (read(open-input-file "starbucks4.sxml")))

(define get-artifacts
  (lambda (l)
   (member (list 'opm:artifact) l)))

When I type get-artifacts(*graph*) I get an error saying procedure application: expected procedure, given:...(the whole of my file contents)

Anyone see what I'm doing wrong? Thanks guys :)

PS: I'm really new to Scheme so it's probably some stupid syntax I'm forgetting!