36. Rhinoceros: 1 species.
The seventh order, Cete, the Whales, consists of four genera:—
37. Monodon, the narwhal, or sea-unicorn: 1 species.
38. Balæna, the whale, properly so called: 4 species.
39. Physeter, the cachalot: 4 species.
40. Delphinus, the dolphin: 3 species.
Including a few additional species mentioned in the appendix to the third volume, and the Mantissa of 1771, the number of Mammalia known to Linnæus was about 230. At the present day, more than 1000 species are described.
The second class, that of Birds, is divided by him into six orders, the essential characters of which are derived from the bill and feet, as follows:—
I. Accipitres: Birds of Prey. The bill more or less curved, the upper mandible dilated or armed with a tooth-like process near the tip; the feet short, robust, with acute hooked claws.