_Lagenorhynchus._[167]—Rostrum scarcely exceeding the length of the cranium, broad at the base and gradually tapering towards the apex, depressed. Pterygoids normal, meeting in the middle line. Teeth small (not exceeding 4 mm. in diameter), ²³⁄₂₃ to ³³⁄₃₃. Vertebræ very numerous, 80 to 90. Spines and transverse processes of the lumbar vertebræ very long and slender; centra short. Externally, head with a short but not very distinct beak. Two species, _L. albirostris_ and _L. acutus_, are occasionally captured on the British coasts. Other species occur elsewhere. _Group B._—Head with distinctly elongated rostrum, or beak, generally marked off from the prenarial adipose elevation by a V-shaped groove. Rostrum of skull considerably longer than the cranial portion. Atlas and axis firmly united; all the other cervical vertebræ free. If we add to it the above-mentioned genus, _Lagenorhynchus_, this group will include all the true Dolphins, Bottle-noses, or, as they are more commonly called by seafaring people, “Porpoises,” which are found in considerable abundance in all seas, some species being habitually inhabitants of large rivers, as the Amazon. They are all among the smaller members of the order, none exceeding 10 feet in length. Their food is chiefly fish, for the capture of which their long narrow beaks, armed with numerous sharp-pointed teeth, are well adapted, but some appear also to devour crustaceans and molluscs. They are mostly gregarious, and the agility and grace of their movements in the water are constant themes of admiration to the spectators of the scene when a “school of Porpoises” is observed playing round the bows of a vessel at sea. _Delphinus._[168]—Teeth very numerous in both jaws, ⁴⁰⁄₄₀ to ⁶⁰⁄₆₀, occupying nearly the whole length of the rostrum, small, close-set, conical, pointed, slightly curved. Rostrum elongated, usually about double the length of the cranial portion of the skull. Pterygoids of normal form, meeting in the middle line throughout their length. Palate with deep lateral grooves. Vertebræ 73 to 75. Pectoral fin of moderate size, narrow, pointed, somewhat falcate. Second and third digits well developed; the rest rudimental. The type of the genus is the Common Dolphin of the Mediterranean (_D. delphis_, Fig. 97), also found in the Atlantic, and of which a closely allied if not identical form is met with in the Australian seas (_D. forsteri_) and in the North Pacific (_D. bairdi_). Other species are _D. janira_, _D. major_, etc. [Illustration: FIG. 97.—The Common Dolphin (_Delphinus delphis_). From Reinhardt.]