270 Diy. 1. VERTEBRATE ANIMALS.— REPTILIA. Class 3. 



The Boas more particularly so named, liave a hook on eacli side of the anus ; a com))ressed hody, 

 larger towards the middle ; a prehensile tail ; and small scales, at least on the hinder part of the head. 

 Among them are found the largest of all Serpents, certain species attaining a length of thirty or forty 

 feet, and heing capahlc of swallowing Dogs, Stags, and even Cattle, at least according to some narra- 

 tors, after having crushed them within their folds, lubricated them with their saliva, and enormously 

 dilated tlicir jaws and gullet. This operation lasts a long while. A remarkable particular of their 

 a'latomy consists in their having one lung but half shorter than the other. [At the extremity of the 

 great lung in all this tribe is an extremely capacious air-bag, the use of which appears to be for con- 

 taining the air requisite for respiration, when the nostrils are closed by the tedious process of degluti- 

 tion.] We subdivide these Serpents according to the teguments of the head and jaws. 



Some have the head covered as far as the tip of the iimzzle with small scales resembling those of the body, and 

 the plates which invest the jaws are not furrowed with grooves. Others have scaly plates beneath the eyes as far 

 as the muzzle, and no furrows to the j.iws. Some, again, have scaly plates upon the muzzle, ami grooves upon 

 those of the sides of the jaws. There are some with plates on the muzzle, and the sides of the jaw hollowed into a 

 slit-like chink beneath the eye and further backward. And, lastly, some have no furrows, and the muzzle 

 invested witli plates but slightly prominent, which are obliquely cut backwards in front and truncated at the tip, 

 so as to terminate in corners : these have the body much compressed, and the back keeled. They inhabit the 

 East Indies whereas the others are from America, and should form a distinct subgenus — Cenchris, Gray. 



The Scytals {Pseudoloa, Schneider). 



Plates, not only on the muzzle, l)ut over the cranium, as in tlie Snakes proper ; no grooves, the body 



round, and head even with the trunk, as in the Roles. 



Daudin has likewise separated 



The Eryx,— 



Wliich differ by having a very short obtuse tail, and by their ventral plates being narrower. The head 



is short and nearly even with the body, characters in which they ap[)roximate the Roles, weie it not 



that the conformation of tlieir jaws permitted tliese to distend. The head is covered with small 



scales ; and they have also no hooks near the anus. 



The Erpetons, Lacepede, — 

 Are very remarkable for liaving two soft prominences covered with scales, at the tip of (he muzzle ; 

 head plated ; the plates of the belly not very wide, and those of the under-part of the tail different 

 from the other scales. Tlieir tail, however, is long and pointed. 



The Snakes Proper {Coluber, Lin.) — 

 Comprehended all the species, venomous or non-venomous, the plates underneath the tail of whicli are 

 divided each into two, or, in other words, ranged in jjairs. 



Independently of the subtraction of the venomous kinds, their number is so vast that we are obliged to have 

 recourse to all sorts of characters in order to distinguish them. First, are separated 



The Pythons, Daudin, — 

 Wliich have hooks near the anus, and narrow ventral plates, as in the Poas, from which they only 

 ditlcr l)y having the plates underneath the tail double. Tlieir head is plated at the tip of the muzzle, 

 and their lips grooved. Species occur as large as any Boa. 



Some of these Pythons have the first, and others the terminal plates of their tail, simple ; but these are perhaps 

 accidental varieties. 



The Vcrheri, like the true Pythons, have the head entirely covered with small scales, with the e,\ception of 

 plates between and before the eyes ; but they have no hooks near the uuus. They liave sometimes also simple 

 plates at the base of the tail. 



Xchopctlis, Keiinvanlt; have great imbricated triangular plates before the eyes, which might be confounded 

 with the scales adjacent to them, only that the latter are smaller. 



J/c^trorfoH, Ueauvois.— The ordinary plates of this group, but the tip of the muzzle composed of a short single 

 piece, in form a trihedral pyramid, which is a little raised and erected above, a conformation which has induced 

 the appellation of pig-snouted Serpents. 



The Ihirrla, Daud.— Indian species, with subraudal plates always simple, except those at the point, which arc 

 double ; these trivial anomalies, however, merit but little notice. 



The Uipsas of Laurenti (Uiiiigarus, Oppel.)— Body compressed, and very much larger than the head: the range 

 of scales along the spine of the back larger than the others. 



DeiutiopliU, l-'itzinger; Aluclidla, Gray.— KcseniblL' the last by having a range of broader scales along the back* 

 and narrower siales along the Hanks; but their heail is not wider than the body, which is slender and very luucb 

 lengtlieued. I^iuzzle obtuse. 



