398 LOWER VERTEBRATES. 



there are about fifteen species, many of which present several local varieties. Although 

 the Australian Acanthophis and many members of the genus Typhlops have the tail 

 terminated by variously foiTaed spines, the ajDpendage peculiar to Crotalus is by far 

 the most interesting, as it is by far the strangest development. As to its use, many 

 have been the theories ; some claim that, as the sound resembles that produced by 

 several insects, it is a lure for insectivorous birds, but observation has shown that, 

 while hunting, the snake ordinarily preserves quiet ; it is moreover seldom that birds 

 are found, on dissection, to be in the stomach. Equally weak seems the explanation 

 that the sound piroduced by the rattle so terrifies the smaller animals on which the 

 snake feeds, as to render them helpless and thus easily captured. To many it might 

 seem probable that it is a special organ designed for bringing the sexes together in the 

 mating season, an end which is often gained by other and numerous means, but, while 

 mating, the rattle, though used, is not vibrated with as much energy as it is when the 

 reptile is irritated, and it is here that we find the probable use of the organ. Though 

 ordinarily perfectly able to defend itself, the rattle-snake is, after having repeatedly 

 drawn from its supply of poison, for some little time comparatively helpless, and being 

 rather slow, as well as having a sullen disposition, it would, were not some provision 

 made, suffer from its temporary helplessness. This is prevented, however, by the 

 rattle, which the snake, on being surprised, uses as an alarm, making its presence 

 known, the reptile thus avoiding the undue waste of poison, which to it is an essential 

 means of protection. 



The rattle, a most common cabinet curiosity, is made up of a series of depressed 

 horny rings, each consisting of a posterior tongue-shaped portion, which is held in the 

 hollow, cup-like, anterior portion of its succeeding fellow by a terminal knob, the so- 

 called ' button.' It will thus be seen that if a portion of the rattle is broken off, a 

 ' button ' will always remain. As such an accident is not infrequent, and since sev- 

 eral new joints may be added during a season, the number of rings can in no way 

 indicate the age of their possessor, though we must give up all hope of this fact ever 

 being comprehended by the ordinary local reporter. 



The habit of rapidly vibrating the tail, when excited, is possessed by many ophi- 

 dians, and when it is done while the reptile is in dry leaves, a noise is produced so 

 resembling the alarm of the rattle as to even deceive an expert. This habit of many 

 harmless forms has often resulted in their death, they being first mistaken for adult 

 rattlers, though, when killed, the excited hero, not finding the terminal appendage, and 

 not willing to allow the mistake, maintains it is a young rattler, an assumption often 

 apparently substantiated by an inspection of the tail, which is often tipped in many 

 innocuous ophidians by a smooth horny scale. 



Crotalus durissus is the introductory species, and is found from Mexico to Brazil. 

 It has often been confused with C. horridus, but is at once distinguished from that 

 animal in that it has the scales arranged in twenty-nine or thirty-one rows, and 

 the dorsal markings more regular and taking on a lozen-shaped form. The keels of the 

 scales are very large and swollen, though, as in O. horridus, they do not arm the 

 outer row of scales, which are large, smooth, and broad. The general color is yellow- 

 ish brown, ornamented along the back by a series of sub-diamond-shaped brown spots 

 with light centres and yellow borders, and which, as they continue to the flanks, enclose 

 rhombs of the general ground color. The yellowish belly is clouded with darker 

 shades. • 



Crotalus molossus is a native of New Mexico and Arizona, and is characterized 



