Saw this beautiful Cactus in Bloom by Vendor .Can some one identify the Cactus for me.

Prabhi S

Looks like an echinopsis. Probably Echinopsis oxygona.

I agree with Echinopsis, but suspect it is 'Los Angeles' a hybrid iso oxygona, though you really cannot tell that easily until the plant grows some more. 'Los Angeles' has some trichocereus genes making that it grows to 3-4x times the size of your average oxygona. There are some flower differences as well, but that is not always easy to distinguish because flowers on these plants are influenced significantly by growing conditions in terms of their appearance.