The Pachycardia are then divided into Monorhina, which contains the cyclostome fishes, distinguished by their single nasal aperture; and Amphirhina, comprising the other Vertebrata, which have two nasal apertures.
"Critiques and Addresses"
Thomas Henry Huxley
His prey is a cyclostome with a graceful spiral shell, tight-closed with a stony lid which is attached to the animal by a powerful muscle.
"The Glow-Worm and Other Beetles"
Jean Henri Fabre