This large, bright red brittlestar is called Ophioderma squamosissimum.
This is a very, very delicate ophiuroid and does not do well in transit. It must be acclimated at every step of the way, from capture, to supplier, to LFS, to buyer, or it will not survive. The acclimation time should be 6-8 hours, using a drip method. This is the best thing to try even if some have had success with shorter periods. Any indication of arms dropping means that the animal is likely very stressed. Most die in transit.
This is a rare species in the wild, and care should be taken that it is given the best chance of survival in captivity. I also recommend spot feeding them, to insure they get enough food. They are not as likely to eat other animals in the tank, like the green brittletar does, but they will eat if they are hungry and can catch something. The specific gravity of the tank should be 1.025 (not the lower ranges often seen). They are very stressed by lower salinities. A stable, mature tank (preferably reef) is key. It is important not to have them with puffers, triggers, wrasses, etc. These are natural predators of brittlestars.