Habitat: Only found in the South Pacific Ocean (subtropical zone), as far as the New Hebrides and the shores of Tasmania.
P. schistorhynchus.—Coloration and size as in P. colubrinus: body with 25-45 annuli.
Habitat: Western Tropical Pacific.
G.—GEOGRAPHICAL DISTRIBUTION OF THE PRINCIPAL GENERA OF POISONOUS SNAKES IN THE FIVE DIVISIONS OF THE WORLD.
| (1) EUROPE. | |||
|---|---|---|---|
| Families | Sub-Families | Genera | Geographical Area |
| Colubridæ | Dipsadomorphinæ | Cœlopeltis | Borders of the Mediterranean in France and Spain; Italy (only in Liguria). |
| Viperidæ | Viperinæ | Vipera | France, Italy, Switzerland, Austria-Hungary, Germany, Belgium, Sweden and Norway, Gt. Britain, Spain and Portugal, Bosnia and Herzegovina, Southern Russia, Turkey and Greece. |
| (2) ASIA. | |||
| Colubridæ | Hydrophiinæ | Hydrus Thalassophis Acalyptophis Hydrelaps Hydrophis Distira Enhydris Enhydrina Aipysurus Platurus | Persian Gulf, Indian Ocean, Bay of Bengal, Straits of Malacca, China Sea, Philippines, and Malay Archipelago. |
| Elapinæ | |||
| Bungarus | India, Ceylon, Burma, Indo-China, Southern China, Dutch Indies, Borneo. | ||
| Naja | India, Ceylon, Burma, Indo-China, Dutch Indies, Philippines. | ||
| Hemibungarus | South-eastern Asia, India, Japan, Philippines. | ||
| Callophis | South-eastern Asia, India, Burma, Indo-China, Formosa, Southern China. | ||
| Doliophis | Indo-China, Malay Peninsula. | ||
| Viperidæ | Viperinæ | Vipera | Turkestan, Ural, Siberia, Caucasus, Persia, Armenia, Western China, India, Ceylon, Himalayas. |
| Pseudocerastes | Persia. | ||
| Cerastes | Arabia, Palestine. | ||
| Echis | Persia, Arabia, India, Baluchistan, Afghanistan. | ||
| Crotalinæ | Ancistrodon | Transcaspia, Turkestan, Himalayas, Southern China, Formosa, Japan, Ceylon, Java. | |
| Lachesis | South-eastern Asia, India, Southern China, Indo-China, Formosa, Sumatra. | ||
| (3) AFRICA. | |||
| Colubridæ | Elapinæ | Boulengerina | Central Africa. |
| Elapechis | Central and South Africa. | ||
| Naja | Egypt, Central and West Africa, Morocco, Congo, Angola. | ||
| Sepedon | South Africa, Cape of Good Hope. | ||
| Aspidelaps | South and South-east Africa, Mozambique. | ||
| Walterinnesia | Egypt. | ||
| Homorelaps | South Africa, Cape of Good Hope. | ||
| Dendraspis | Central and South Africa, Angola, Great Lakes, Congo, Transvaal. | ||
| Viperidæ | Viperinæ | Causus | West Africa, Gambia, Great Lakes, Congo, Angola, Transvaal. |
| Vipera | Morocco, Algeria, Tunis, Egypt, Mozambique. | ||
| Bitis | Zanzibar, Zambesia, Cape, Transvaal, Congo, the Gaboon, Benguella, Angola, Senegal, Nigeria. | ||
| Cerastes | North Africa, the Sahara. | ||
| Echis | North Africa, Lake Chad, Soudan, Egypt, Somaliland, Socotra. | ||
| Atheris | Tropical Africa, Dahomey, Lagos, the Cameroons, the Gaboon, Congo. | ||
| Atractaspis | Tropical and South Africa, Congo, Angola, Lake Chad, the Gaboon, Dahomey, Gold Coast, Zanzibar, Somaliland, Natal, and the Cape. | ||
| (4) OCEANIA. | |||
| Colubridæ | Hydrophiinæ | Hydrus Thalassophis Hydrelaps Hydrophis Distira Enhydris Enhydrina Aipysurus Platurus | Equatorial and Sub-tropical Pacific Ocean, the Moluccas, Papuasia, New Guinea, Celebes, Timor, Australia, Tasmania, New Caledonia, New Hebrides. |
| Elapinæ | Ogmodon | Fiji Islands. | |
| Glyphodon | Northern Australia, New Guinea. | ||
| Pseudelaps | Australia, the Moluccas, Papuasia. | ||
| Diemenia | Australia, New Guinea. | ||
| Pseudechis | Australia, New Guinea. | ||
| Denisonia | Australia, Solomon Islands, Tasmania. | ||
| Micropechis | New Guinea, Solomon Islands. | ||
| Hoplocephalus | Australia. | ||
| Tropidechis | Australia. | ||
| Notechis | Australia, Tasmania. | ||
| Rhinhoplocephalus | Australia. | ||
| Brachyaspis | Australia. | ||
| Acanthophis | Moluccas, Papuasia, Northern Australia. | ||
| Elapognathus | Australia. | ||
| Rhynchelaps | Australia. | ||
| Furina | Australia. | ||
| (5) AMERICA. | |||
| Colubridæ | Elapinæ | Elaps | Mexico, Central America, Bolivia, Ecuador, Peru, Colombia, Brazil. |
| Viperidæ | Crotalinæ | Ancistrodon | North America, Florida, Texas, Mexico, Guatemala. |
| Lachesis | Central and South America, Martinique, St. Lucia. | ||
| Sistrurus | North America east of the Rocky Mountains, Mexico. | ||
| Crotalus | Southern Canada, British Columbia, Central America, Guiana, Venezuela, Brazil, Uruguay, Northern Argentina. | ||
PART II.
CHAPTER IV.
SECRETION AND COLLECTION OF VENOM IN SNAKES.
Non-poisonous as well as poisonous snakes possess parotid and upper labial glands capable of secreting venom. In the former the organs of inoculation are wanting, but we shall see later on that the toxic secretion of their glands is just as indispensable to them as to the snakes of the second category for the purpose of enabling them to digest their prey.
For the morphological, histological, and physiological demonstration of the existence of these glands in harmless reptiles we are indebted to Leydig (1873), whose discovery has since been confirmed and extended by the researches of Phisalix and Bertrand, Alcock, L. Rogers, and L. Lannoy.
The parotids of Grass Snakes are mixed glands of the sero-mucous type. The serous tubes are situate almost exclusively in the posterior portion of the gland. As we proceed towards the anterior portion, we find that these serous tubes are interspersed with others which are exclusively mucous or sero-mucous, and they become entangled with those of the upper labial gland, properly so-called. The substance of the gland is divided into several lobes by bands of connective tissue; the tubes are separated by septa of the same tissue, in extremely delicate layers (Lannoy).
In poisonous snakes these glands are much more developed, especially in their hinder portions, which sometimes assume enormous dimensions. They may attain the size of a large almond (Crotalus, Naja), and they then occupy the spacious chamber already described (Chap. I., p. 10), which is situated behind the eye on each side of the skull.