This small family, consisting of the genus Atractaspis, is also confined to Africa, but has hitherto only been found in the West and South.
Family 23.—HYDROPHIDÆ. (8 Genera, 50 Species.)
| General Distribution. | |||||
 | |||||
| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| — — 3 — | — — — — | — — — — | — — — 4 | 1. 2. 3. 4 | 1. 2. 3. 4 |
The Hydrophidæ, or Sea Snakes, are a group of small-sized marine serpents, abundant in the Indian and Australian seas, and extending as far west as Madagascar, and as far east as Panama. They are very poisonous, and it is probable that many species remain to be discovered. The genera are distributed as follows:—
Hydrophis (37 sp.), ranging from India to Formosa and Australia; Platurus (2 sp.), from the Bay of Bengal to New Guinea and New Zealand; Aipysurus (3 sp.), Java to New Guinea and Australia; Disteira (1 sp.), unknown locality; Acalyptus (1 sp.), South-west Pacific; Enhydrina (1 sp.), Bay of Bengal to New Guinea; Pelamis (1 sp.), Madagascar to New Guinea, New Zealand, and Panama; Emydocephalus (1 sp.), Australian Seas.
Family 24.—CROTALIDÆ. (11 Genera, 40 Species.)
| General Distribution. | |||||
| |||||
| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| 1. 2 .3. 4 | 1. 2. 3. 4 | — — 3. 4 | — — — — | 1. 2. 3. 4 | — — — — |
The Crotalidæ, or Pit Vipers, including the deadly Rattlesnakes, form a well-marked family of fanged serpents, whose distribution is very interesting. They abound most in the Oriental region, at least 5 of the genera and 20 species being found within its limits, yet they are quite unknown in the Ethiopian region—a parallel case to that of the Bears and Deer. A few species are peculiar to the eastern portion of the Palæarctic region, while the Nearctic is actually richer than the Neotropical region both in genera and species. This would point to the conclusion, that the group originated in the Indo-Chinese sub-region and spread thence north-east to North America, and so onward to South America, which, having been the last to receive the group, has not had time to develop it largely, notwithstanding its extreme adaptability to Reptilian life. The genera are divided among the several regions as follows:—
Craspedocephalus (7 sp.), Tropical America and the West Indian Islands; Cenchris, Crotalophorus, Uropsophorus, and Crotalus, inhabiting North America from Canada and British Columbia to Texas, one species (Crotalus horridus) extending into South America; Trimeresurus (16 sp.), all India from Ceylon to Assam, Formosa, the Philippines and Celebes; Peltopelor and Hypnale (1 sp. each), peculiar to India; Calloselasma (1 sp.), Siam; Atropos (1 sp.), Java and Borneo; Halys (3 sp.), peculiar to Tartary, Thibet, Japan, North China, and Formosa.
Family 25.—VIPERIDÆ. (3 Genera, 22 Species.)