Distribution—The cottonmouth has been reported in the following counties: Anderson, Aransas, Atascosa, Austin, Bandera, Bexar, Bowie, Brazos, Brazoria, Burleson, Burnet, Cass, Calhoun, Chambers, Cherokee, Collin, Colorado, Comal, Dallas, Denton, Ellis, Falls, Fannin, Fisher, Fort Bend, Galveston, Goliad, Gonzales, Grayson, Guadalupe, Hardin, Harris, Harrison, Hays, Henderson, Houston, Jasper, Jefferson, Kaufman, Kerr, Kimble, Lamar, Leon, Liberty, Limestone, Marion, Mason, Matagorda, Maverick, McLennan, Medina, Montgomery, Morris, Nacogdoches, Newton, Nueces, Orange, Parker, Polk, Red River, Refugio, Robertson, San Jacinto, San Patricio, Shelby, Smith, Sterling, Tarrant, Tom Green, Travis, Uvalde, Val Verde, Victoria, Walker, Wharton, Wilson, and Wise. The cottonmouth is one of our largest poisonous snakes. It is particularly abundant in the coastal marshes of southeastern Texas where it is found along streams, ponds and lakes. Although ordinarily rather sluggish, it immediately draws back its head and opens its mouth widely in a threatening manner when annoyed, exposing the white tissue lining the inside of the mouth. This characteristic pose is responsible for its popular name. Moreover, like the copperhead, which also lacks rattles, it has the habit of vibrating its tail when sufficiently annoyed. Thus, when it is among dry leaves, or if the tail strikes a hard object, the resulting sound may be similar to that made by a rattlesnake. The name water moccasin, which is loosely applied to any and all water snakes as well as to the cottonmouth, has resulted in a popular but misplaced belief that all “water” snakes are poisonous. It should be pointed out here that the cottonmouth, _Agkistrodon piscivorus leucostoma_, is our only poisonous aquatic serpent. The several kinds of harmless water snakes, which in some instances resemble it, are devoid of poison. They can, at most, inflict a bite no more serious than the scratch of a cat and these wounds require only the first aid recommended for minor cuts. Harmless water snakes most frequently mistaken for the cottonmouth include the large diamondbacked water snake of central and eastern Texas, the blotched water snake found over most of the state, and the yellowbellied and broadbanded water snakes of eastern Texas. Most of them are relatively heavy bodied, possess somewhat diamond shaped heads and, although not venomous, will bite viciously if stepped upon or handled. THE RATTLESNAKES