Discussion Forum—A Way with Words, a fun radio show and podcast about language

I have a question regarding the use of the colon after the word by and before the name of a writer -- and, while I'm in the neighborhood, the capitalization of the word "by." An example would be centered on the cover page of a student's paper, as in

Echoes of the Cold War

By: Stella Howe

My sensibilities regarding grammar and writing conventions tell me that "by" is a preposition, which is immediately followed by its object. Am I correct, or is this a special case.