410 REPORT OF NATIONAL MUSEUM, 1893. 



1872 paired on January 21, 1873, and on the following July 6 he found 

 8 recently-born young in the cage. They were about 260 mm. long by 

 15 mm. thicli, and, unlike the parents, of a pale flesh color, with black- 

 ish brown zigzag bands. After the first molt, about two weeks after 

 birth, the ground color became more reddish brown, and at the next 

 one, about five weeks later, copper brown, the head being more brightly 

 colored in all stages. This color lasted into the second year, when 

 they gradually assumed the dark color of the parents. During the 

 first two weeks they took no food, then they accepted young frogs, but 

 refused fishes. At the end of two months they were 340 mm. long, 

 with a proportionally large head. The parents seemed to show some 

 affection for their offspring. 



Genus SISTRURUS,* Gamiaii. 

 The Ground Rattlesnakes. 



1822. — CrotaJiis, Fleming, Philos. ZooL, ii, p. 294 (type C. miUaris) (not of Linn., 



1758). 

 1825.— Crotaloplwr Its, Gray, Ann. Philos., 1825 (p. 205) (not of Honttnyn, 1764). 

 1826.— Cattdisoiia, Fitzinger, N. Class. Rept., p. 34 (type C. miliarius) (not of 



Lanrenti, 1768). 

 1883.— Sisirunts, Garman, N. Amer. Rept., I, Ophid., pp. 110, 176 (same type). 



Between 1822 and 1826 several authors, led by Fleming, for the first 

 time undertook to subdivide the old genus Croialns into two genera 

 according to the scutellation of the top of the head, but they were 

 very unfortunate in adopting for the ground rattlers names which had 

 been used before. Considerable confusion in the nomenclature of the 

 rattlesnakes was the result, as partly pointed out under the head of 

 Grotalus. S. Garman was the first to fully understand the situation, 

 and, in 1883, to supply a tenable name for the genus of the ground 

 rattlers. He has fully demonstrated the correctness of his position.t 



The Ground Rattlesnakes form a small compact genus of only three 

 species, one of which is confined to Mexico. Their distribution in the 

 United States is rather curious, inasmuch that they are found in the 

 eastern portion east of the Rocky Mountain region proper, although 

 one form enters the Sierra Madre plateau, even occurring on the west- 

 ern slope of it in Arizona. 



The two species inhabiting the United States occupy two distinct 

 areas, which only overlap to a comparatively slight extent in the 

 Indian Territory and adjacent region. 



Synopsis of the species of Sisirurns fo:ind in Die Vnited States. 



«'. Prefrontals not in contact with the loreal proper (lowerloreal, if two be present) ; 

 a whitish stripe from posterior nasal below eye to angle of nionth (fig. 45). 

 &'. Number of scale rows usually 25. 



c'. Spots larger S. catenalus 



c^ Spots smaller ^ S. c. consors 



*From the Greek anarpor (seistron), a rattle; ovpa (oura), a tail, 

 t Science, xix., May 20, 1892, p. 290. 



