356 REPTILES. OPHIDIA. 



es of this jaw are also not united ; and those of the upper jaw are united to the 

 intermaxillary only by ligaments. From this structure these animals have the faculty 

 of dilating their jaws, so as to swallow bodies thicker than themselves. Their pala- 

 tine arches participate in this mobility, and are armed with sharp teeth curved 

 backwards, one of the most constant characters of the tribe. 



These serpents are naturally divided into those which are poisonous and those 

 which are not ; and these again may be subdivided into poisonous serpents with 

 many maxillary teeth, and poisonous serpents with isolated fangs. In those not 

 poisonous, the jaws and the palatine branches have fixed and solid teeth ; four rows of 

 these teeth, nearly equal, being in the upper part of the mouth, and two rows be- 

 low. 



1. Body cylindrical ; tongue short. 

 Gen. 6. TORTRIX, Oppel. Anguis, Lin. 



Scales of the belly and under the tail larger than the others ; 

 tongue thick and short ; tail extremely short. 



T. scytale, Oppel. Body fulvous, with irregular black and white 

 rings. From 1 to 2 feet long. S. America Shaw, iii. 581. 



T. corallinus, Cuv. Body pale red, with broad alternate bands and 

 variegations of deep coral-red. 18 inches long. Inhabits South 

 America. Shaw, iii. pi. 131. 



T. ater, Cuv. Body white, with black bands. Inhabits S. Ame- 

 rica. Shaw, iii. pi. 132. 



T. maculatus, Cuv. Body yellowish or orange-coloured, with an 

 alternately fasciated black dorsal band. 18 to 20 inches long. 

 Inhabits South America. Shaw, iii. 585. 



2. Occiput more or less gibbous ; tongue forked and exten- 

 sible. 

 Gen. 7. BOA, Lin. 



Anus with a hook on each side ; body compressed, thickest in 

 the middle ; tail prehensile ; scales small, at least upon the 

 posterior part of the head. 



The largest of serpents, some species reaching thirty or forty feet in length, and 

 swallowing dogs, deer, and even oxen, according to some travellers. This genus 

 formerly comprehended all serpents, poisonous and not poisonous, of which the bo- 

 dy and tail were furnished with transverse scaly bands, and which had neither 

 spur nor rattle at the end of their tail. 



B. constrictor, Lin. With a long chain-like line, formed alternate- 

 ly by large blackish spots, irregularly hexagonal, and pale oval 

 spots, hollowed at their ends, running along the back. 20 to 35 

 feet long. India, Africa, and S. America. Shaw, iii. pi. 92, 93. 



B. cenchris, Lin. The Ringed Boa. Body fawn-coloured, with a 

 chain of large brown rings along the back, and variable spots on 

 the sides. 265 abdominal plates, 57 subcaudal. 20 feet long. 

 Inhabits Surinam. Shaw, iii. pi. 94. 



B. scytale, (and murina,) Lin. The Anaconda. Body bright- 

 brown ; a double row of deep brown round spots along the back ; 



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