Some of you seem to be VERY confused about the difference between a euphonium and a baritone.
A euphonium is actually larger. They both have the same length of tubing and play the same pitches, but the difference is in the shape of the tubing. A euphonium's tubing starts getting bigger almost immediately whereas a baritone's tubing stays the same diameter until almost the end. It's like the difference between a cornet and a trumpet. The number of valves is immaterial.
Euphonium on the left, baritone on the right. Or, to put it in terms bass players can understand, euphonium is in front of the bergantino, baritone is in front of the acmes.
In the US, we also have an instrument that's a cross between the two -- usually called an "american baritone" or sometimes also "baritone horn". These are pretty rare and really only beginners and old guys in community bands play them. An american baritone is closer to a euphonium than it is to a true baritone.
This is an example of an american baritone:
http://www.kingwinds.com/content/detail.php?item=627
Note that even the manufacturer is a little confused, calling it a euphonium at the top of the page and a "baritone horn" in the text...
A lot of the confusion comes from the fact that even a lot of euphonium players erroneously call it a "baritone" -- and a lot of music, especially older music, will say "baritone" on it. It's really a euphonium.
The original picture that was posted was, in fact, a euphonium.