Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Fish 7.25): The capitone fish, as he says [i.e. Liber rerum], is very small, rarely so large as to grow half a foot. And this one indeed has a name from its nature: for it has a large head [Latin capito] almost as large as the rest of the body. This fish, living in rivers, lives under stones and among rocks. It has a large mouth and a round head. These fishes signify those who, hearing with a perfect and best heart (and grasping with eager desire), retain the word of God and bear fruit in patience. - [Badke translation/paraphrase]

Vincent de Beauvais [circa 1190-1264 CE] (Speculum naturale, Book 17.40): The capito is a very small fish, having a head almost as large as the rest of its body, and a round and large mouth, which, living in rivers, willingly hides under stones and among rocks. - [Badke translation/paraphrase]