The buttons and data knobs are recessed and reinforced by double aluminum construction.
Dorsal vertebrae frequently have a ventral outgrowth of the centrum; these hypapophyses may be simple vertical blades, I-shaped, or paired knobs; they serve for the attachment of the thoracic origin of the longus collianticus muscle, reaching their greatest development in Sphenisci and Colymbidae.
Fore-wings well developed; hind-wings reduced to stalked knobs (" halteres ").
The [ox's] horns are of nearly equal size in both sexes, are placed on or near the vertex of the skull, and may be either rounded or angulated, while their direction is more or less outwards, with an upward direction near the tips, and conspicuous knobs or ridges are never developed on their surface.
In the males the horns are usually compressed and triangular, with transverse ridges or knobs, and either curving backwards or spiral.