Tetra a tall dorsal fin characterized by a short connection to the fish’s body. Additionally, tetras possess a long anal fin stretching from a position just posterior of the dorsal fin and ending on the ventral caudal peduncle, and a small, fleshy adipose fin located dorsally between the dorsal and caudal fins. This adipose fin represents the fourth unpaired fin on the fish (the four unpaired fins are the caudal fin, dorsal fin, anal fin, and adipose fin), lending to the name tetra, which is Greek for four. While this adipose fin is generally considered the distinguishing feature, some tetras (such
Operculum (gastropod) the shell of "Charonia tritonis" is a seal made by the Minoan civilization. Opercula of certain gastropods, especially varieties from the Red Sea, have long served as an incense material in ancient Jewish tradition, as well as Arabian cultures. The operculum of conch species "Strombus tricornis" and "Lambis truncata sebae" are most commonly used in regions near the Middle East. Opercula from these conches may be the onycha incense material which is described in the Book of Exodus. Operculum powder is also an important ingredient in Chinese and Japanese incense making. Here it is called ""bèi xiāng"" (Chinese: 貝香; "lit."