it's better when played backwards^^

Base +5, GodMan7 +8, perunamuussi -6, Chicken Boo +6, Seelenmord -10, Ms. Black Fire#10018 +6

Lamia, not naga, nagas are human face on completely snake body.

Base +6, Seelenmord -10, 00devo00 -6, Ms. Black Fire#10018 -6

Only in the D&D monster manuals, Kithrin

Base +6, RavenOfTheDarkAbyss +8, Ms. Black Fire#10018 +6

tl;dr version: Both Lamia and naga are wrong, so use whichever one you feel like. If you want to be picky, Lamia is the more correct of the two. (Also, not biased, because I prefer the term naga, personally)

Actually, the original naga were mythological creatures that were simply giant snakes. Though as many things in mythology, the definition has blurred greatly, the most common change was to make naga multi-headed serpents rather than single headed ones. The use of a human torso on a snake body is a creation largely of modern times. Even with "human forms" of nagas in the past, it was generally fully human with a snake head over their head or simply fully human. Interestingly, there's a picture from Hindu mythology that depicts a naga having been slain by Krishna, where the naga's wives were all human-torso-on-snake-body, but they weren't called nagas in the story. This picture may be where the modern usage comes from, though. And fun fact: naga is the masculine. A female naga is technically a nagi or nagini.

That said, Lamia isn't technically the most accurate term either. The original Lamia was the queen of Libya, as told in Greek mythology, who was cursed by Hera. Accounts vary, but some myths don't even make her a monster (in appearance), or just a bit disfigured. Others make her out to be a four-legged creature without a human torso, just breasts and a human head. Originally, she was famous for her tendency to eat babies (either because Hera made her crave babies, or because she went insane after Hera killed hers, the accounts, again, vary). Unlike naga, though, the term "lamia" has meant a creature with the torso of a woman and a body of a snake for several hundred years, often being associated with the occult, being treated as creatures halfway between succubi and vampires (ie, something that will both seduce you and suck your blood).

So basically, neither one is really accurate, but the term "lamia' has been used in this incorrect fashion for longer. That said, I prefer the term naga for my snake-girls. Since both are wrong, but both are used in this way in contemporary usage, both are right, in their own way. Naga are not generally pictured with human'ish faces, except in D&D, but that's only because D&D made them more human that their actual mythology.

Sources:
http://en.wikipedia.org/wiki/Lamia <--Lamia mythology
http://en.wikipedia.org/wiki/N%C4%81ga <-- Mythological naga (as opposed to the dozens of pop culture hits)
http://en.wikipedia.org/wiki/Kaliya <-- story about the naga's wives

Base +5, BattleJesus +6, 00devo00 -6, goodeats1337 +6, Ms. Black Fire#10018 +6