Trigeminal adj. (Anat.) Of, pertaining to, or designating, the fifth pair of cranial nerves, which divide on each side of the head into three main branches distributed to the orbits, jaws, and parts of the mouth; trifacial.
... all, at least in the sense in which the words have hitherto been used" (p. 571). The membranous or cartilaginous skull of these fishes shows a general resemblance in its main features to the ossified skull of other Vertebrates; the relations of the ear to the vagus and trigeminal nerves are, for instance, the same in both; the main regions of the cartilaginous skull can be homologised with definite bones or groups of bones in the bony skull; but discrepancies occur. It is again to development that we must turn ... — Form and Function - A Contribution to the History of Animal Morphology • E. S. (Edward Stuart) Russell