"Underbelly" was a very polite way of putting it S :)
But it's definitely the back end of the Big Merino in Goulburn, and it's definitely a boy!
According to Miss Tizz, the top picture clearly illustrates the merino's brain. The backstory to that comment is that a few years ago, she and the X-man were in the bath together. Miss Tizz was quiet for a while (highly unusual!), then suddenly burst out with "Why does he have a brain under his willy?". Of course, that was followed by "Where's my willy and my second brain?".