Description Gallery Bibliography Manuscripts Jump to Home page Help Jump to Contents page Jump to Beast Index page Search Previous beast Next beast

Source: British Library Digital Catalogue of Illuminated Manuscripts Copyright Copyright 2004 British Library / Used by permission Manuscript description British Library, Royal MS 12 C. xix, Folio 12v



Latin name: Hydrus

Other names: Enhydros, Enidros, Hildris, Hydra, Idra, Idres, Ydre, Ydris, Ydrus

The enemy of the crocodile, which it kills from the inside


General Attributes

The hydrus is an animal that lives in the Nile River. It is the enemy of the crocodile. When it sees a crocodile sleeping with its mouth open, the hydrus first rolls in mud to make itself slippery, then enters the crocodile's mouth and is swallowed. It then eats its way out of the crocodile's belly, killing it.

There is considerable confusion in applying the name hydrus and its variations to beasts. The root of the word itself refers to water, and this led to several beasts, mostly serpents, being so labeled. Isidore of Seville lists the hydros, a water snake that causes those bitten to swell up, the cure for which is the dung of an ox. The hydrus was also confused with the hydra of the Hercules legend, some texts saying that it was a many-headed water dragon, living it the swamp of Lerna, that could grow new heads; the legend actually refers to a water fountain that sprouted new outlets when one was blocked.


The crocodile signifies hell, and the hydrus Christ, who descended into hell to recover imprisoned souls.

Sources (chronological order)

Isidore of Seville [7th century CE] (Etymologies, Book 12, 2:36): The enhydros is a small animal; it gets its name because it lives in water, specifically the Nile river. If it finds a sleeping crocodile it first rolls in mud, then crawls into the crocodile's mouth; after eating all of the crocodile's inner parts it comes out of the beast, killing it.

St Antony of Padua [12th-13th century CE] (Sermons): The apostles are compared to ichneumons. There is a certain little serpent which rolls itself in the mud, and thus enters the mouth of the sleeping crocodile, who wakes up and swallows it down; on which it eats through his entrails, and comes out through his side. Thus the Apostles, rolled as it were in the mud of poverty and humility, leapt boldly into the mouths of tyrants, and openly contradicted their words of unbelief, and were thus devoured by death. Nevertheless, these tyrants themselves were slain by their means, and the Apostles came forth alive from them, when their death redounded to the augmentation of the faith and to the honour of Christ. (MediŠval preachers and mediŠval preaching: A series of extracts, translated from the sermons of the middle ages, chronologically arranged; with notes and an introduction (London, 1856) Neale translation)


The hydrus is almost always illustrated with its tail sticking out the crocodile's mount and its head emerging from the crocodile's side. The Icelandic Physiologus (ArnamagnŠanske Institut, AM 673a 4║) depicts the hydrus as a bird, with feathers in the crocodile's mouth and a bird's head emerging from its side. A few bestiary manuscripts show the hydrus as a snake; the hydrus in British Library, Harley MS 3244 (f. 62r) is shown as a water snake swimming beside a man in a boat.

Description Gallery Bibliography Manuscripts Jump to Home page Help Jump to Contents page Jump to Beast Index page Search Previous beast Next beast