56 REPTILES AND BIRDS. 
The Natal Rock Snake (7. xatalensis, Fig. 13) is described by 
Sir Andrew Smith as being gigantic in size, he having seen a skin 
measuring twenty-five feet, although part of the tail was absent. 
“Tt feeds,” he says, “‘on small quadrupeds ; and for some days after 
swallowing one it remains in a torpid state, when it may be easily 
destroyed.” Of this opportunity, however, the South Africans never 
avail themselves;*they have a horror of the reptile, but believe 
that it has an influence over their destinies, and affirm that no one 
has ever been known to kill one and prosper. 
The Guinea Rock or Fetish Snake (H. Scbe, Fig. 14) is typical 
of the genus, and has also been referred to the Boa Constrictor, and 
closely resembles the Natal Rock Snake.* It is a native of the 
warmer parts of Africa. A living specimen at the Zoological Gardens 
is estimated to weigh a hundredweight. 
Of the genera Zzasis and LVordoa there are five species, very 
imperfectly known. 
I1V.—picrates, an American and West Indian species, having 
the crown scaly, the forehead with symmetrical shields. 
The Aboma (Z. cenchria, Fig. 15) is one of the largest of the 
group, sometimes attaining dimensions quite gigantic. It is yellowish 
in colour, with a row of large brown rings running the whole length of 
the back, and variable spots on the sides; these are generally dark, 
with a whitish semi-lunar mark. ‘This formidable reptile has all the 
habits of its congeners ; it is found in the marshy swamps of tropical 
America and near the rivers, where it lies in wait for its prey. 
The Boas, properly so-called, have the scales smooth; labial 
shields smooth, not pitted; the body compressed, tapering to the 
tail, which is long and prehensile ; the head is comparatively small, 
being enlarged behind and contracted towards the muzzle, which is 
rather short. The crown is covered with scales ; the nostrils lateral, 
between two plates. Four species of this genus are recognised by 
naturalists, all of which have been described by travellers as the true 
Boiguacu, or boa constrictor of Linnzeus. This species has the scaly 
circle of-the orbit separated from the upper labial plates by one or 
two series of scales. A large chain consisting of blackish hexagonal 
spots, alternating pale oval stains, notched and jagged, extending 
the whole length of the back, and forming a very elegant design. 
This species seems to be strictly confined to tropical America, 
Humboldt found it in Guiana, and the Prince de Wied observed it 
* A variety very similar to this is known in China,—Eb, 
