 The mouth of the holotype of Corythosaurus is narrow . The praemaxillae each form two long folds . The folds <unk> air passages extending the narial passages to the front of the snout . There they end in narrow openings , sometimes called " pseudonares " , false bony nostrils . These were mistaken by Brown for the real nares or nostrils . These are actually situated inside the crest , above the eye <unk> . As in Saurolophus , the expanded portion of the premaxillary in front of the <unk> ' opening is <unk> : by comparison , in Kritosaurus , the bill is short , and the pseudonares extend far forward . At the end of the Corythosaurus bill , the two pseudonares unite into one . Because of his incorrect identification , Brown assumed that the holotype 's inferior process of the premaxillary was shorter than in Kritosaurus and Saurolophus , and that the process does not unite with the <unk> , another difference from those genera . The <unk> actually does touch the <unk> and extends to the rear until well behind the eye <unk> . 
