Although they're up over the past two weeks, gas prices have fallen dramatically since nearing the $4-a-gallon mark. But it's not showing in falling sales for hybrid and alternative-fuel vehicles yet, says Kelley Blue Book.

Poring over the sales charts, Kelley, aka KBB.com, found sales of hybrids and alternative-energy vehicles surged more than 164% in June. If gas prices fall again, the car pricing service notes, it could suck hybrid and alternative fuel vehicle sales down with it. It hasn't yet.

Among the sales stars:

Toyota Prius, helped by three new versions -- the c small car, v wagon and a plug-in -- tripled its sales compared with June of last year. It helped, too, that there were adequate supplies of cars, unlike last year in the aftermath of the Japanese tsunami and earthquake.

Lexus CT200h sales were up about 500% year-over-year.

Chevrolet managed to double sales of its Volt extended-range electric sedan. Says KBB: "The Volt has outsold the Nissan Leaf nearly 3-to-1 so far this year, even though it has a higher manufacturer's suggested retail price and is not considered a 'true' all-electric from a purists' standpoint."

It wasn't true all around. Honda CR-Z, Honda insight and Nissan Leaf all saw sales fall.