Erechtheus and His Daughters (page 247 upper)

DOG: He is said to have been given by Jove as a guardian for Europa, and later to have come to Minos. When Minos was ill, Procris, wife of Cephalus, is said to have cured him, and received the dog as a reward for her services, as she was very fond of hunting and the dog was so swift that no beast could escape. After her death the dog came to Cephalus her husband, who brought it to Thebes with him when he came. There was a fox there which was said to be so swift that it could outrun all dogs. So when the two animals met, Jupiter, in a dilemma, as Istros says, changed them both to stone.

§ 2.35.2  Some have said that this is the dog of Orion, and because Orion was devoted to hunting, the dog was put with him among the stars. Others have called it the dog of Icarus. These many suggestions have their own advocates.

§ 2.35.5  The Dog has one star on his tongue which itself is called Dog, and on its head another which Isis is thought to have put there under her own name, and to have called it Sirius on account of the brilliance of the flame because it seems to shine more than the rest. So, in order for men to recognize it more easily, she called it Sirius.  Latin Text