The Gannets or Boobies are black and white, or brown and white, birds of considerable size, inhabiting the open sea and living upon fish. They have a powerful pointed bill and the outer nostrils are completely closed in adults. There are 18 cervical vertebras; the ambiens, femoro-caudal and semi-tendinosus muscles are present, the two accessory thigh-muscles absent; there are no syringeal muscles.
Some recent authors, Mathews especially, has divided the Sulidae into many genera, nearly every genus containing but one species. Mathews relies on certain characters such as the reticulation or scutellation of the tarsus and toes which, admittedly, differs in nearly every species but the very fact that it differs so constantly seems to prove that it is not of generic value. I prefer to retain all our Indian species in the one genus, Sula.