_Tursiops._[169]—Rostrum tapering moderately from base to apex; palate not grooved; symphysis of mandible short; other cranial characters as in _Delphinus_. Teeth ²¹⁄₂₁ to ²⁵⁄₂₅, stout (6 to 7 mm. in antero-posterior diameter). Vertebræ: C 7, D 13, L 17, C 27; total 64. Limbs as in _Delphinus_. Represented by the widely distributed _T. tursio_; _T. catalania_ being a second form. Fossil remains of this genus from the Italian Pliocene have been recently described. _Prodelphinus._[170]—Rostrum somewhat variable; mandibular symphysis short (less than one-fifth the length of the ramus); other cranial characters as in the preceding genus. Teeth ³⁰⁄₃₀ to ⁵⁰⁄₅₀, small, not exceeding 3 mm. in diameter. Vertebræ 73 to 78. Limbs as in _Delphinus_. Four leading types of this genus are recognised (all of which have numerous synonyms) viz. _P. obscurus_, _P. euphrosyne_, _P. doris_, and _P. longirostris_. Péron’s Dolphin (_Delphinus leucorhamphus_, Péron, or _Leucorhamphus peroni_, Lilljeborg) resembles some forms of _Prodelphinus_ in its cranial characters; but having no dorsal fin, it has been separated generically by some writers. It is not improbable that _Delphinus borealis_, Peale, from the North Pacific, in which there is likewise no dorsal fin, may be an allied form. _Steno._[171]—Rostrum long, narrow, and compressed, very distinct from the cranium; mandibular symphysis as long as, or longer than one-fourth the length of the ramus; other cranial characters as in the preceding genus. Teeth ²¹⁄₂₁ to ²⁵⁄₂₅, of comparatively large size (5-6 mm. in diameter); surface of their crowns finely grooved. Vertebræ: C 7, D 12, L 15, C 32; total 66. Represented by _S. rostratus_, from which the forms which have received other names are probably not specifically separable. _Sotalia._[172]—Pterygoids narrow, not meeting in the middle line, and in their inner borders diverging posteriorly, instead of being parallel as in the preceding genera; other cranial characters much as in _Steno_. Teeth tolerably large (4-5 mm. in diameter), ³⁰⁄₃₀ to ³⁵⁄₃₅, with smooth enamelled surface. Vertebræ: C 7, D 12, L 10-14, C 22; total 51-55. Pectoral fin broad at base, the breadth being caused by the considerable development and position of the two outer digits. Six species are provisionally recognised as distinct, including the Chinese White Dolphin (_S. sinensis_) and _S. pallidus_ from the river Amazon.