Teeth various; sometimes entirely wanting: body fish-shaped: anterior extremities in the form of fins; posterior united, forming a flat horizontal tail.
* Grinders with flat summits: nostrils at the ex-tremity of the snout, not acting as blow-holes: whiskers very distinct: mammce pectoral.
Grinders eight or nine on each side above and below; with two transverse ridges on the summits: no incisors or tusks in the adult state: vestiges of nails on the margins of the pectoral fins.
A single grinder on each side above and below; summit flat with projecting plates of enamel: fins without vestiges of nails.
** Teeth, when present, conical: nostrils opening on the crown of the head, acting as blow-holes: whiskers none: mammce near the anus.
† Head small: blow-holes united.
Both jaws with numerous teeth, all simple and equal.
(1. Delphinus). Snout produced into a beak, broad at its base, rounded at its extremity, and separated from the forehead by a kind of furrow: a dorsal fin.
(2. Phoccena). Snout short and blunt; not beaked : a dorsal fin.
(3. Delphinaptera). Head blunt; snout not produced: no dorsal fin.
Head blunt: no true teeth; upper jaw with one, rarely two, very long straight tusks projecting forwards in a line with the body: no dorsal fin.
Snout produced: teeth generally but two in number, placed in front of the lower jaw: palate studded with tubercles: a dorsal fin.
††Head very large; half or one third of the entire length.
Head enormously large, truncated in front: upper jaw without whalebone or visible teeth; teeth in the lower jaw numerous: blow-holes united.
(1. Catodon). No dorsal fin.
(2. Physeter). An elevated dorsal fin.
Head very large: palate furnished with whalebone: no teeth : blow-holes separate.
(I. BalAEna). No dorsal fin.
(2. BalAEnoptera). A dorsal fin.