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Show 1867.] DR. H. BURMEISTER ON PONTOPORIA BLAINVILLII. 485 only 3 lines long, and the last 10 lines. The spinous processes are not very high, but tolerably broad ; the anterior one much inclined; the posterior directed more perpendicularly, and double the breadth of the former. The transverse processes decrease in length from the first to the seventh, but increase in breadth ; and from there to the tenth they become again longer, as well as broader, the tenth being 16 lines long, and the seventh only 7 lines. Each of these processes has a projection on the anterior margin near the base, and an oblique truncated tip, to which the rib is articulated. The seven lumbar vertebrae are the largest and strongest of all, the first being 11 lines long and the seventh 12 lines. All have high and large spinous processes, which become somewhat higher posteriorly, so that the three last lumbar vertebrae are the highest of all. The transverse processes of these same vertebrae are extremely broad, and not directed forwards as in the typical Dolphins, but rather backwards : near the base on the fore and hinder margin of each process is a prominent tubercle, which is stronger on the fore margin than on the hinder; and by these projections the processes are united to each other. Even on the fourth, fifth, and sixth lumbar vertebrae the tubercles overlap each other, the hinder of the anterior vertebra lying upon the fore ones of the posterior (see fig. 1), and Fig. 1. Pontoporia blainvillii. The second and third lumbar vertebrae, natural size, seen from below. a a. Second vertebra, b b. Third vertebra. forming in this manner a sort of secondary articulation between the vertebras, which must make the movement of the lumbar portion of the body very strong, and the vertebral column, if contracted, very firm. The eighteen caudal vertebrae are of very different form and size, and have together a length of 9 inches 8 lines. The first five have inferior spinous processes, and the same, with the sixth, also superior spines; but each one is somewhat smaller and lower than the foregoino-. The transverse processes are much shorter than in the lumbar portion, and do not touch each other with their tuberosities ; they soon become smaller, and lose their prominent tip. This decrease is so rapid, that already the fifth caudal vertebra has no |