The Procellariiformes, or Petrels, are archaic ocean forms with great powers of flight, often placed near the Laridae on account of a supposed external resemblance, though the structure of the internal parts shews this to be misleading, and indicates rather a position between the Sphenisciformes and Ciconiiformes. The single Sub-Order TUBINARES, with the Family _Procellariidae_, may be subdivided into the Sub-families: (1) _Diomedeinae_, or Albatroses; (2) _Oceanitinae_ and (3) _Procellariinae_, or Fulmars, Shearwaters, and Petrels proper; and (4) _Pelecanoïdinae_, or Diving Petrels.[63] Fam. PROCELLARIIDAE.–In the larger species the bill is long, stout, and frequently compressed, with a strong sharp hook overhanging the truncated mandible; its size gradually diminishing throughout the Sub-Families in very much the above order. The {60}horny sheath is separated by grooves into more or less distinct plates, and the mandible may also be grooved, as in _Phoebetria_; while _Prion_ is especially remarkable for the curious fringe of transverse lamellae on the margins of the broad maxilla, which recall those of the Duck tribe, traces of the same being exhibited by _Ossifraga_, _Fulmarus_, _Daption_, and _Halobaena_. The most striking peculiarity, however, is the tubular structure of the impervious nostrils, which trenchantly divides the Petrels from all other Birds; these tubes are far apart in the Diomedeinae, and lie laterally towards the back of the culmen; in the remaining groups they are fused together and are situated dorsally. In the Oceanitinae the single aperture looks forwards and upwards, but in the Procellariinae the septum is produced to the front, showing clearly the double nature of the formation; in _Pelecanoides_ again the distinct openings are almost vertical, an arrangement as well adapted to the diving habits as are the long sternum and the compressed wing-bones. The rows of retroverted spines found on the palatal membrane in most of the family no doubt aid in the retention of slippery prey, as do the lamellae in _Prion_. The lower portion of the tibia is bare; the metatarsus varies in length and stoutness according to the species, though often decidedly slender, and is much compressed in _Puffinus_ and its nearest allies. It is usually covered with hexagonal scales, but _Oceanites_ and _Cymodroma_ show but one long anterior scute (_ocrea_), while _Garrodia_ and _Pelagodroma_ have a series of oblique plates instead. The hallux is absent in _Pelecanoides_, and consists of only one phalanx elsewhere, being quite rudimentary in the Diomedeinae; it is slightly above the level of the anterior toes, which are connected by large webs. The claws are, as a rule, sharp, curved, and compressed, but are blunt and much flattened in _Pelagodroma_, _Pealea_, and _Cymodroma_, showing a similar tendency in others of the Oceanitinae. The wings are normally long, and are very narrow and pointed in the Diomedeinae, where the expanse is vast, but in