Dictionary of Ichthyology  

naris (plural nares) = the nostril. External nares open onto the head, internal nares connect the nasal cavity with the mouth cavity (as in Dipnoi). The median naris of Myxini also opens into the mouth. In other fishes the naris on each side is single and leads into a blind sac or the nares are double and connected to one another, via the olfactory chamber.
Nares of Acanthias divided by a moveable flap (A) and in a  young Amia showing anterior (n) and posterior n1 openings (B), from Kingsley's "Textbook of Vertebrate Zoology, 1906. Photograph by Brian W. Coad.d.

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