Sources : Tyrus

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Serpents 8.42): Tyrus, as Jacobus says, is a serpent in the region of Jericho, about the deserts of Jordan. The snake is hostile to birds and animals, and especially to the eggs of birds, which it certainly eats and swallows with the birds themselves. Its flesh is prepared as an electuarium [electuary, medical prescription] with some of it mixed in, which drives out and eradicates all toxic poisons. This confection is called tyracca [theriaca, a medical panacea]. Some say that before Christ's passion this snake had no remedy and was especially vicious to men, but that it happened on the very day that Christ was hung on the cross, that one of these most vicious snakes was seized around the region of Jerusalem, and hung by the side of Christ on the cross; and from that day every species of the serpent itself received the power in the shedding of the blood of Christ, the most effective remedy against all poison. Aristotle: There is a kind of dragon in that land, where there are tyrus [tyri] serpents in the land of Ethiopia, and from it Tychicus receives a kind of poison, which is an irremediable evil. But while tyria are effective against all poisons, nothing is effective against the poison of the tyri itself, which is called tychicon. A tyrus is a serpent which, worn out in old age, casts off its skin in this manner: first it peels off the skin that is between the eyes, so that, if you did not know, you would think it a blind beast. Then it takes off the skin of the head, and this in one night and one day. But when the head is stripped, the rest of the body is easily stripped. But when it has been stripped, it has the manner and behavior of an embryo. There is a certain species of tyri, a less than cubit in length, with hairs all over the body, whose bite rots the wound round about, and from time to time kills. The Indian tyrus is destructive beyond measure. The tyrus ovulates inside, and before it comes out, it becomes a live animal, and begets something like itself. - [Badke translation/paraphrase]

Bartholomaeus Anglicus [13th century CE] (Liber de proprietatibus rerum, Book18.9; 18.116): [Book 18.9] Also Arist[otle] saith, li. 3. Tyrus the Serpent gendereth beastes within, but shée hath first egges within, and of the egges beasts be bred within: therefore it is said, yt the mother of the other Serpents is long, after the making of the body. And their mother beginneth in ye nether part, and passeth up in either side of the ridge boane, and is divided in two partes, and hath as it were a wall or interclose betweene the two partes, and therefore the two Egges be set arowe in the mother. And a Serpent layeth not all her egges at once, but some & some. Also lib. 5. Aristotle saith, yt in tune of gendering Serpents wrappeth and clippeth themselves together, that they séeme one body with two heads, as it is knowen to them that have séene the doing. Also libr. 7 Aristotle sayeth, that a Serpent, and namelye Tyrus, when he swalloweth a Birde or ought else, first he areareth himselfe, and afterward restrayneth himselfe until the thing that he swalloweth passe inward, and that is for his stomacke is little and smal. And Serpents may live long without meate, as it is knowen by Serpents that are kept to sell. [Book 18.9] And Tyrus is a maner serpent that is called Vipera also. Of him Aristotle speaketh lib. 8. and saith, That Tirus right as the Crocodile, hideth him in winter, and doth afterward off his skin that is betwéene his eyen, and they that know not the doing, wéene that hée is blinde, and then he doth off the skin of his head all in one day: and his flaieng and passing out of his skin, is as the passing out of a childe of the mothers wombe, and he is by that manner renued, and putteth away, and is so delivered of his age. Moreover, in the same booke, in the ende thereof it is found, that it is sayd in this wise: Great Serpents flye this serpent Tirus though he be little, and all his body is rough, and when he biteth anye thing, all that is about the thing, rotteth anone. And one little serpent called Tirus is found in Inde, and his biting is so strong, that against it no medicine can be found. - [Batman]