SCALED REPTILES— THE RATTLE-SNAKES. 429 



winter months ; and in certain rocky districts they were formerly wont to 

 assemble in enormous numbers, passing the winter huddled up together in 

 caves where they kept one another warm. At the approach of the cold 

 season, thousands of these snakes might be seen travellnig from all points of 

 the compass to their own special cave ; and marvellous stories have been 

 told of attacks made upon these haunts when the hapless reptiles were sleep- 

 ins in fancied security. It is somewhat curious that rattle-snakes lack the 

 power of hissing ; and it is highly probable that this disability has some 

 connection with the presence of the rattle. Nearly allied to the rattle-snakes 

 is the equally deadly bushmaster {Lachesis mutus) of tropical South America, 

 which has a spine in place of a rattle at the tip of the tail, while the lower 

 surface of the latter bears a number of spmy scales. There is often a well- 

 marked keel running down the middle of the back, of which there is no trace 

 in the typical genus. This snake is one of the few serpents which do not flee 

 at the presence of man, always standing its ground and endeavouring to m- 

 flict a blow. Since it frequently grows to ten feet and over, and its bite is 

 rapidly fatal even to large mammals, it is one of the most dangerous of its 

 tribe, and were it more common than it actually is, fatalities would be very 

 numerous. By Mr. Boulenger the serpents formerly designated Trigono- 

 cephalus and Trimeresaurus are now included in Lachesis. These differ from 

 the typical forms in having the whole of the top of the head covered with 

 small scales, instead of large scales. Some species are arboreal, and have 

 the tail prehensile ; some of these inhabiting Tropical America, and others 

 South-Eastem Asia. Whereas the species from the latter area have two 

 rows of shields beneath the tail, those from the former have only a single 

 row. Among the American forms with a non-prehensile tail, one of the most 

 formidable is the jai-araca (L. lanceolatus). 



The so-called halys vipers, forming the genus Ancistrodon, have represen- 

 tatives alike in the northern half of the American Continent and Asia, while 

 one kind is found in the Ural Mountains. Although none have a rattle, in 

 some kinds there is a small spine at the tip of the tail, which appears to be 

 a vestige of that organ. Of' the Transatlantic species one of the most 

 dreaded, and at the same time one of the handsomest, is the so-called 

 copper-head (A. contortrix). It takes its name from the metallic coppery, 

 hue of the upper surface of the body ; this ground-colour being ornamented 

 with a number of brown bands with darker edges. The copper-head, which 

 frequents damp situations, has a wide geographical distribution. It is one 

 of the species furnished with a spine-like horny appendage to the tail ; and 

 differs from some of its kindred in having a single instead of a double series 

 of shields on the under surface of the tail. 



ORDER IV.— RHYNCHOCEPHALIA. 



If we were to trust solely to external features a lizard-like reptile inhabiting 

 certain small islands to the north-eastward of New Zealand, and locally 

 known as the tuatera, would almost certainly be included in the order Squa- 

 mata. When, however, the internal structure of this creature is examined, 

 differences so important are observable that there can be no question of its 



