Opuntia robusta?

Is this a specimen of Opuntia robusta or is it some other species? I used to have Opuntia robusta few years ago but it seemed not quite the same as this plant, thanks.

It looks like mine. The pic of the full plant was taken 09.25.2009. It is quite huge now and I have had to prune it due to the weight and interfering with yard space and movement. xuling

DMersh, It is Opuntia engelmannii
http://davesgarden.com/guides/pf/go/65218/

What is this Opuntia please?

Thanks for replies, I thought O Engelmanii had green pads, or at least not blue, but if Xenomorph says thats what it is I'm not going to argue!
Nancy your Opuntia looks like O basilaris?

Hi Nancy, I agree with DMersh, opuntia basilaris.

Thank you for the help!

DMersh, here's an O. engelmannii that's about the same color as yours
http://davesgarden.com/guides/pf/showimage/278188/

Yes, they do look about the same. I assume O engelmannii would be a bit hardier than O robusta, being from a more northerly habitat, think O robusta is central Mexican in origin.
this was start of a new pad.

I can see Xuling's plant is much less spiny than mine, though you do get spiny varieties of O robusta. Not surprising it got bit out of hand, O robusta can do a lot of growing in 4 years, especially if in the ground. Mine was sold as O robusta 'Cuerva' but I can't seem to find any reference to this variety beyond the nursery where it was bought (Kuentz cactus nursery in France).

I found a page where it shows photos of what they are calling it a cultivar 'Cuerva'.
One this page they mention that "the spination is close to that of O. engelmannii f. discata"
http://palmaris.org/html/oprob.htm
Without extensive data showing the areas of occurrences in the wild to sway my thinking, It could very well be a form of O. engelmannii, or an intermediate or hybrid with O. rubusta.
But then you are intermingling the different forms and cultivars and the same specimen my end up with different names..
So, I will stick with just plain O. engelmannii, for now.

I took a much closer look at the spination of both yours and the samples on that link, and I "do" see some similarities, even though yours is less spinier. Again though, distribution data would help greatly with this.

I think on the whole the spines do look more like O engelmannii, maybe in the wild there's some overlap between O robusta and engelmannii.

I think my plant is Opuntia basilaris as DMersh said from the pictures here in PlantFiles. Mine blooms pink just like those and it does not have long spines at all.

Definitely no spines on O basilaris.