Thats O. erincea isnt it?
Lovely flowers, how big/old is the plant?

Nice flower there Baci, gotta love those Opuntia flowers, the spine are another thing though. :)
Larry, the common name Mojave prickly pear is given to Opuntia phaeacantha (at least according to Desert Tropicals).

The spines do not bother me  at least I know where they are & they are easy to pick out.

I am unsure about the age. The picture with the flower is a cold hardy cactus; native to the high Sierras; about 5000 ft. elevation.

I believe the botanical name is optunia erinacea var. erinacea. According to the book Native Cacti of CA by Benson, the distinction of the varieties of Optunia erinacea from those of O. polyacantha is not clear cut on the basis of flattening of at least the basal portions of the larger spines in O. erinacea. It can hybridize when in contact with var. erinacea and O. polyacantha var. rufispina. These cacti can also include genes of var. erinacea, var. utahensis, & O. polyacantha var rufispina.

Here is another one located at the Rancho Santa Anna botanic garden (near Los Angeles). On their sign for the Mojave prickly pear are the words: "O. erinacea var. erinacea. Spine length and color are extremely variable. Some are ornamental."

{{gwi:478827}}

Yep, that's erinacea, Larry nailed it! I have a small cutting of that one that I'm trying to establish, plus a seed grown erinacea v. ursina (which has the brownish spines), I posted a pic of it yesterday.
The problem with common names is just that.. they're common! and can apply to more than one species.
That's a very nice pic Baci!

CP.

CP, heres my erinacea,lovely cactus:

{{gwi:478828}}

How low a temp can it take?

Nice cactus, GreenLarry. The spines on these cacti is what makes them striking. The one at the top is from an elevation of maybe 5,000-7000 ft, and can tolerate cold to zero degrees Fahrenheit. I think that is about 17 degrees Celsius. The two I posted are seldom exposed to freezing temperatures & stay outside all the time.

I saw your erinacea v. ursine yesterday, Cactuspolecat. I have been trying to find that one in nature so I can get a photograph of it. Thanks for the complement on the photo  it was by my wife. Mine are not as sophisticated.

You're welcome, Baci. I'd love to see a habitat shot of ursina, I reckon that'd be really neat!
Just in response to larry's query about temperatures, my ursina is entirely glasshouse grown and winter temps in there get to 0 degrees celsius and below (-1 to -2 ish).

CP