I tend to go with "this is the first time I have submitted as (a) but I have previously been publishing under another pseudonym/the name of (b)" depending on how the market in question is likely to feel about the other name's writing. It shows you've been published - hence, you can string sentences together - but doesn't draw too much attention to what you've published, since as far as they're concerned just because you can write one genre doesn't mean you'll be a shoo in for another.