Amongst birds worshipped by the Egyptians, one of the most important was the ibis. It was associated with Thoth and the moon, and in the earliest period the city of Hermopolis was the centre of this cult. A passage in Herodotus gives many interesting details concerning the ideas held regarding the bird. He tells us that he went to a certain place in Arabia, near the city of Buto, to learn about the winged serpents, brought into Egypt by the west wind, which the ibis was believed to destroy along with the ordinary reptiles common to the country. Arriving there, he "saw the backbones and ribs of serpents in such numbers as it was impossible to describe; of the ribs there were a multitude of heaps, some great, some small, some of medium size. The place where the bones lie is at the entrance of a narrow gorge between steep mountains, which there opens upon a wide plain communicating with the great plain of Egypt. The story goes that, with the spring, the winged snakes come flying from Arabia toward Egypt, but are met in this gorge by the birds called ibises, who bar their entrance and destroy them. The Arabians assert, and the Egyptians admit, that it is on account of this service that the Egyptians hold the ibis in so much reverence. The ibis is a bird of a deep black colour, with legs like a crane; its beak is strongly hooked, and its size that of the landrail. This is a description of the black ibis which contends with the serpents." Another bird held in great reverence was the bennu, a bird of the heron species which gave rise to the mythical bird, the phœnix. It is identified with the sun, a symbol of the rising and the setting sun. Many fables arose concerning this bird, and are recounted by Herodotus and Pliny. Another sun-bird was the falcon, sacred to Horus, Ra, and Osiris, and this was worshipped throughout Egypt in the pre-dynastic period. In another form, represented with a human head, it was symbolic of the human soul, a distinction it shared with the heron and swallow, in both of which it was believed the human soul might reincarnate itself. Plutarch says that it was in the form of a swallow that Isis lamented the death of Osiris. Also sacred to Isis was the goose, though one species of it was devoted to Amen-Ra; while the vulture was the symbol of the goddesses Nekhebet and Mut. There is some evidence to prove that certain fish were held as sacred, and worshipped because of their mythological connexion with divers gods and goddesses. Sacred Trees