THE PYTHONS AND BOAS 2551 



southward it likewise diminishes in numbers in lower Brazil. Feeding principally 

 upon birds, the dog-headed boa is an excellent swimmer, and has been observed 

 both in the Rio Negro and in the salt water of the beautiful harbor of Rio de 

 Janeiro. Although it frequently visits the huts of the Brazilian negroes in 

 search of prey, it does not appear that this snake ever voluntarily attacks human 

 beings. If, however, it is driven to bay and unable to escape, it is capable of 

 inflicting very severe bites with its long front teeth, such wounds being difficult 

 to heal. 



A third genus of tree boas (Enygrus) is distinguished from both 

 Keeled t ^ e preceding by the scales having distinct keels; the labial shields of 



the head being devoid of pits, and the tail short and prehensile, with 

 a single row of shields on its inferior surface. This genus is represented by four 

 species inhabiting the Moluccas, the Papuan region, and Polynesia. 



This gigantic snake is the sole member of a group of several 



genera, distinguished from the tree boas by the teeth gradually 

 decreasing in size from the front to the back of the jaws without any marked 

 enlargement of those in the fore part. Merely mentioning the allied tropical 

 American genera, Trachyboa, Ungalia, and Ungaliophis, the first and last of which 

 are each represented only by a single species, we may observe that the anaconda is 

 specially distinguished as a genus by the large size of the rostral shield of the head, 

 behind which one pair of the nasals come in contact with one another in the 

 middle line, and by the very small size of the smooth scales of the body. The 

 head is markedly distinct from the neck; the nostrils are directed upward and 

 placed between three pairs of nasal shields, of which the hindmost are those which 

 meet in the middle line; the small eye has the pupil vertical; the body is 

 cylindrical, and the tail is short and slightly prehensile, with a single row of 

 shields inferiorly. In color the anaconda is grayish brown or olive above, with 

 either one or two series of large blackish transverse spots, and a single or double row 

 of lateral eye-like spots having whitish centres and blackish rims. The upper part 

 of the head is dark and divided by a black streak, terminating in a point on the 

 muzzle, from the lighter cheeks; while another oblique black streak runs on each 

 side behind the eye; the under parts being whitish with blackish spots. 



The anaconda (Euneces murinus) is an inhabitant of the Guianas, Brazil, and 

 Northeastern Peru, and is essentially an inhabitant of tropical forest regions. That 

 it is the largest of all living snakes there can be little doubt, but the precise limits 

 of size to which it may occasionally attain cannot be ascertained. A stuffed ex- 

 ample in the British Museum has a total length of twenty-nine feet, and the species 

 is commonly stated to reach thirty-three feet, while, if native reports are to be 

 trusted, individuals of much larger size are occasionally met with. Although nat- 

 uralists are generally indisposed to credit the existence of monsters of forty feet, 

 or even more, we confess that personally we are unable to share their incredulity, 

 as it is very improbable that the largest specimens have come under European ob- 

 servation. From all accounts, it appears that the anaconda generally spends more 

 of its time in the water than on land, frequently floating down rivers with the 

 current, and at other times lurking in quiet pools with only its head raised 



