I'm a little confused about the wording of Girallon's Blessing.
First of all, it describes the new pair of arms as "Secondary Limbs", but I'm not sure what this means. Does it mean that the claw attacks from the new arms are secondary natural attacks? I would think not, since all of the claw attacks deal 1d4 + Str modifier damage and secondary natural attacks normally only get 0.5x Str modifier to damage; also the spell text makes no mention of the normal -5 attack bonus modifier for secondary natural attacks. However, I don't know what else this would mean.
Also, how does this spell interact with existing claw attacks? Say I cast this on a Black Bear animal companion, for example - does he now just have two extra 1d4 claws, or does it "downgrade" his existing claws?
Does the claw damage scale with creature size?
Finally, could a character wield a shield with one of the new/secondary arms, in order to get both the shield bonus and have both primary arms free for claw attacks?