Moving to El Capitan? Then you need Mono version 4.2.x or 220.127.116.11.
From the Mono mailing list:
What is the difference between the latest Mono 18.104.22.168 package for Mac and the 4.2.1 El Capitan Preview? The changelog of 22.214.171.124 includes “33585: El Capitan System Integrity Protection support.” so i suppose that the 126.96.36.199 also works on El Capitan?.
Reply from Miguel de Icaza:
One is based on Mono 4.0 series, with minimal changes just to enable the support on El Capitan; The 4.2 has the same changes, on top of the latest Mono 4.2, available on Alpha and the release candidate.