420 REPTILTA ORDER IH.SQUAMATA. 



of which the teeth in the fore part of the jaws are superior in size to those be- 

 hind, while the head is covered with shields, the scales on the body are smooth, 

 and there are, at most, but shallow pits in the so-called labial shields of the 

 muzzle. All the members of the genus are inhabitants of Tropical America, 

 the largest not exceeding seven feet in length. The presence of deep pits in 

 the labial shields serves to distinguish the species of the nearly allied genus 

 Corcdlus, of which four are from Tropical America, while the fifth is found in 

 Madagascar. Four other snakes from the Moluccas, New Guinea, and 

 Oceania, constitute the genus Enygrus, which differs from both the preceding 

 in having ridges on the scales of the body. These boas do not appear to 

 molest human beings, but the case is different with the anaconda (Eunectes 

 murinus) of Tropical America, which grows to thirty feet or more in length. 



In common with three other genera from the same countries, two of 

 which are respectively represented by a single species, while the third in- 

 cludes several, the anaconda differs from all the foregoing in that the front 

 teeth are not greatly enlarged, the whole series gradually diminishing in 

 height from before backwards. Among the distinctive generic characters of 

 the anaconda may be noticed the small size of the scales. Its general colour 

 is olive or greyish-brown on the upper surface, upon which are one or two 

 rows of large, dark, transversely- elongated blotches, and one or two of eye- 

 like spots on the sides. The anaconda is essentially a water-snake, and in 

 those parts of its habitat which are subject to a long period of drought, it 

 buries itself in the dried river mud till the return of moister conditions. In 

 the anaconda one of the pairs of shields on the head, technically known as 

 nasals, come into contact with one another in the middle line behind the 

 muzzle, but in the nearly-allied snakes forming the genus Boa a median line 

 of small scales separates all the nasal shields. Of the seven species of true 

 boas, five are from the warmer parts of Central and South America, whereas 

 the other two are met with in far distant Madagascar. The common boa-con- 

 strictor (Boa constrictor) has 

 a wide geographical range, 

 being found from Venezuela 

 to the inland districts of the 

 Upper Argentine. Although 

 marvellous stories are current 

 as to the rapacity of this 

 species whose maximum 

 length is about a dozen feet 

 it appears that its usual 

 Fig. 22. -BOA CONSTRICTOR. f OO( j con sists of the smaller 



mammals, while even eggs are 



sometimes swallowed. It will, however, occasionally attack and kill deer or 

 peccaries. All its victims are destroyed by the crushing effect of the com- 

 pression of the encircling folds of the body. A snake from a small island 

 near Mauritius, forming the genus Cdsarea, differs from the true boas in having 

 distinct keels on its scales, as well as in the greater relative length of the tail. 

 The only other members of the family that can be noticed are the sand- 

 snakes (Erifx) of South-Eastern Europe, Asia, and North and East Africa, 

 which differ from the boas in the want of any distinct line of demarcation 

 between the head and neck. These snakes derive their name from frequent- 

 ing open sandy districts, where they frequently enter the burrows of small 

 mammals and lizards for the purpose of preying on their rightful occupants. 



