Caudal mucous pit on some species included: Caudal mucous pit The caudal mucous pit, or caudal mucous horn, is an anatomical structure on the tail end of the foot of various land snails and slugs, terrestrial pulmonate gastropod mollusks. The function of this pit is the resorption of mucus when the gastropod is moving (see also Muratov 1999). An incorrect and yet often-used term for this structure is the "caudal gland". This area also used to be referred to by the term "caudal pore". Families of snails and slug where a caudal mucous pit exists in every species included: Families/subfamilies where is caudal
Parapterois more (18–21) pectoral fin rays than "Pterois" (12–17), and, in the former, these rays may be branched, while they are never branched in "Pterois". "Parapterois" have two anal fin spines, while "Pterois" have three. Also, as a more obvious trait, the caudal fin of these fish are truncated with longer upper and lower caudal fin rays, while the caudal fin in "Pterois" is rounded. "Parapterois" are native to the Indian Ocean and the West Pacific Ocean. Despite the popularity of other lionfish, "Parapterois" species are only rarely found in the aquarium trade. "P. heterura" can be found on certain online