Wherever Matthew is mentioned, whether in books or websites, sooner or later one usually comes across a statement along the lines of:
Matthew always believed that he, not Darwin, deserved credit for the theory of evolution by natural selection — he even had “Discoverer of the Principle of Natural Selection” printed on his calling cards. [Patrick Matthew biography hosted at U. Berkeley]
The reference to calling cards is likely an urban myth which has endured because it is a nice sounding story. There is no primary evidence that Matthew ever had calling cards made saying this or anything else. The urban myth is traceable back to Loren Eiseley’s influential book “Darwin’s Century: Evolution and the Men Who Discovered It” (1958). Eiseley appears to have misinterpreted a comment that Darwin makes in a letter to Hooker of 22 & 28 Oct 1865. Darwin was in fact referring to a statement that Matthew made on the title page of his 1864 booklet “Schleswig-Holstein”. To confuse matters still further, Darwin had got the statement wrong. Matthew had in fact placed the statement “Solver of the problem of species” on his title page. For more details see Darwin’s letter to Hooker.
Of course, making this statement does suggest a certain degree of theatricality on Matthew’s part, but not as much as putting it on calling cards would imply.