Rattlesnake
2 of the 7 encyclopedias on this shelf carry an entry for Rattlesnake. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a venomous serpent of America, allied to the viper, moccasin, and copperhead. The tail of the rattlesnake is provided with horny rings that rattle together when shaken. The number of rings increases with age, but not with regularity. The rattlesnake has no regular teeth, but possesses a long poison fang on each side in front, at the roots of which are poison sacs. These teeth lie flat when the animal is not enraged. When disturbed the rattlesnake throws himself into a coil, shakes his rattles, and darts or springs at his enemy. We have fourteen species in North America . One species is confined to the Pacific coast. Five species are found only in the southwest or near the Mexican border. The diamond rattlesnake, so named from three rows of diamond-shaped areas on its body, is the largest species of all. It attains a length of eight and one-half feet and an extreme body girth of fifteen inches. It is at home among the palmetto palms of Texas and the Gulf States. The prairie rattlesnake belongs to the Great Plains. This is the species that haunts the old burrows of the prairie dog . The common or timber rattlesnake is found in rocky localities from New England to the Rocky Mountains and southward. It feeds on birds, squirrels, and such animals as may be taken unaware. It brings forth nine to fourteen young alive. It attains a length of three to eight feet. On the approach of autumn, colonies crawl into crevices in the rocks together and lie torpid until spring. The following from Bret Harte has much truth in it: I only know thee humble, bold. Haughty, with miseries untold, And the old curse that left thee cold, And drove thee ever to the sun On blistering rocks Thou whose fame Searchest the grass with tongue of flame, Making all creatures seem thy game, When the whole woods before thee run, Asked but-when all is said and done-- To lie, untrodden, in the sun!
Collier's New Encyclopedia (1921)
the English name for any species of the American genus Crotalus, the tail of which is furnished with a rattle. Garman enumerates 12 species and 13 varieties, falling into two groups: (1) Having the upper side of the head covered with nine dermal shields; (2) having the shields behind the eyes broken up or replaced by small scales. The second group comprises the more formidable kinds, generally described as C. horridus and C. durissus. The first name was formerly applied to HEAD OF RATTLESNAKE A POISON GLAND B FANGS B 8 RATTLESNAKE the reptile extending from Paraguay and Chile through Brazil, into Mexico, and the latter to the North American rattlesnake. In recent American works this nomenclature is reversed. The poison of the rattlesnake is usually fatal to man, though fortunately they are sluggish, and never attempt to strike unless they are molested. They are widely distributed on the American continent.