Fam. VII. LARIDAE.–This consists of four Sub-families (1) _Stercorariinae_ or Skuas, (2) _Larinae_ or Gulls, (3) _Rhynchopinae_ or Skimmers, and (4) _Sterninae_ or Terns. Mr. Saunders[196] is, however, probably right in distinguishing a second Family, _Stercorariidae_; and possibly a third, _Rhynchopidae_, might be admitted. In the _Larinae_ the strong, horny bill is of moderate length, though exceptionally small in _Rhodostethia_, the maxilla being curved, but hardly hooked; in the _Stercorariinae_ there is a distinct hook, and the base is covered by a cere, said to be hard or soft according to the season, and possibly, shed after the manner of certain Auks.[197] In the _Sterninae_ the beak is nearly straight and {301}pointed, while comparatively slender; in the _Rhynchopinae_, the maxilla, which moves vertically with ease, is much shorter than the mandible, and both are compressed anteriorly until they resemble truncated knife blades. The tibia is generally partly bare; the metatarsus is fairly long in the first two Sub-families, and is scutellated in front, being usually smooth behind, though rougher in _Pagophila_; the anterior toes are fully webbed, with claws which vary from weak to moderate, or even to strong and hooked, as in the _Stercorariinae_. The elevated hallux is joined by a membrane to the inner toe in _Leucophaeus_, and is rudimentary or absent in _Rissa_. In the _Sterninae_ and _Rhynchopinae_ the metatarsus is short–especially in the latter, where the web between the inner and middle digits is deeply incised, as are both webs in _Hydrochelidon_ and _Gygis_; the claws are long, slender, and curved. The pointed wings, excessively lengthened in the two last-mentioned Sub-families, have eleven primaries, of which the outer is particularly small, and from fifteen to twenty-three secondaries. The tail may be nearly even as in _Larus_, deeply forked as in _Sterna_ generally, less excised as in _Xema_, _Hydrochelidon_, _Naenia_, and _Rhynchops_, graduated or cuneate as in _Rhodostethia_, _Anous_, and _Gygis_; all the twelve feathers being rounded or acute: in the _Stercorariinae_ the two central rectrices project beyond the others, being decidedly pointed in _Stercorarius crepidatus_ and _S. parasiticus_, but rounded and twisted in the shaft until the webs are vertical in _S. pomatorhinus_. The furcula is U-shaped, the syrinx tracheo-bronchial, the tongue lanceolate, the nostrils are pervious; an after-shaft is present, while both adults and young have abundant down, that of the latter commonly shewing a mixture of white, with grey, yellowish, slaty, or brown. _Naenia_ has elongated plumes at the gape, and a few Terns have slight nuchal crests.