Gallon pints. These pints are divided into two cups (though the imperial cup is rarely used now), which in turn are divided into two gills (gills are also rarely used). Thus a gallon is equal to four quarts, eight pints, sixteen cups or thirty-two gills. The imperial gill is further divided into five fluid ounces, whereas the US gill is divided into four fluid ounces. Thus an imperial fluid ounce is of an imperial pint or of an imperial gallon, while a US fluid ounce is of a US pint or of a US gallon. The imperial gallon, quart, pint, cup
External gills salamander species, such as most members of the Proteidae family (the olm and mudpuppies) and the Sirenidae family, which naturally never metamorphose into an air-breathing form. The embryos of frogs and caecilians also develop external gills at some point in their development, though these are either resorbed before or disappear shortly after hatching. Fossils of the distant relatives of modern amphibians, such as "Branchiosaurus" and "Apateon", also show evidence of external gills. The external gills commonly consist of a single stalk (rami) protruding from a gill arch behind the head of the animal, above an associated gill slit. The stalk