Here a picture of one: [link|http://www.musickidsonline.com/TaraBaritoneUkelele.htm|Baritone Uke.]
It's tuned D, G, B, E just like a the 4 higher pitched (i.e. physically lower) strings of a standard guitar.
I mention it only so that if you are looking for books, sheet music, teacher, whatever for it, you'll find it.
I happen to have one, unsed for years.
HTH