Dictionary of Ichthyology  

exolaterals = small teeth between the endolaterals (near the mouth opening) and the marginals (which line the margin of the disc) in lampreys (Petromyzontidae).

Petromyzon marinus disc, St-Vallier, Fleuve St-Laurent, Québec, CMNFI 1995-0022, 4.7 cm wide without fimbriae. Photograph by Brian W. Coad, image manipulation by Noel Alfonso.

©Canadian Museum of Nature