The lacunolabial scale is a large scale that forms in some crotaline snakes (pitvipers) when the prelacunal scale fuses with the second (rarely the third) supralabial scale. In such cases it is often said that "the second labial enters the pit."[1]
References
^ Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. 2 volumes. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.