_Cogia._[143]—Teeth of the upper jaw absent, or reduced to a rudimentary pair in front; in the lower jaw 9 to 12 on each side, rather long, slender, pointed, and curved, with a coating of enamel. Upper surface of the cranium concave, with thick, raised posterior and lateral margins, massive and rounded at their anterior terminations above the orbits. Upper edge of the mesethmoid forming a prominent sinuous ridge, constituting a kind of longitudinal septum to the base of the great supra-cranial cavity. Rostrum not longer than the cranial portion of the skull, broad at the base, and rapidly tapering to the apex. Zygomatic process of the jugal styliform. Mandible with the symphysis less than half the length of the entire ramus. Vertebræ: C 7, D 13 or 14, L and C 30; total 50 or 51. All the cervical vertebræ united by their bodies and arches. External characters not well known, but, judging by the somewhat conflicting accounts of those that have had an opportunity of observing them, the head is about one-sixth of the length of the body, and obtusely pointed in front; the mouth small, and placed far below the apex of the snout; the spiracle crescentic, and placed obliquely on the top of the head anteriorly to the eyes, and to the left of the middle line; the pectoral fins are obtusely falcate; and there is a triangular dorsal fin. The history of this genus is a good illustration of the difficulties in which the study of the Cetacea has been involved by the superficial manner in which it has been investigated. The first known example, a skull from the Cape of Good Hope in the Paris Museum, was described by De Blainville under the name of _Physeter breviceps_. This was afterwards with good reason generically separated by Gray. Until within a very few years ago only five other individuals had been met with, each of which had been described under a different specific name (viz. _grayi_, _macleayi_, _simus_, _floweri_, and _potsii_), and which are arranged by Gray in two distinct genera. The most careful examination of the description given of these specimens, or of the now numerous osteological remains available, fails to detect any differences beyond those which may be attributed to age or sex, and hence, according to our present knowledge, these six supposed species must all be included under one name, _C. breviceps_. This animal appears to attain the length of 10 feet when adult, and has been met with at various distant localities in the Southern Ocean, and also off the coast of Madras and in the North Pacific.