SAUEIANS. 99 



Snakes, having movable maxillary bones, and mandibles not joined 

 by a symphidis, are enabled to swallow other animals of appa- 

 rently greater bulk than their own. In the Saurians the maxillae 

 are fixed and immovable, and the mandibles are joined by an 

 osseous suture, so that the cleft of the mouth can be dilated only 

 in the usual vertical direction. Moreover, in these limbless 

 Saurians we always find bones of the shoulder hidden below the 

 skin, whilst no trace of them can be discovered in the true Snakes. 

 The motions of some Lizards are extremely slow, while those of 

 others are executed with very great, but not lasting, rapidity. 

 Many of them have the power of changing their colours, which 

 depends on the presence of several layers of cells loaded with 

 different pigments ; these layers the animal compresses by more 

 or less inflating its lungs, whereby the changes in the coloration 

 are effected/' 



Dr. Giinther does not follow Dr. Gray in arranging all 

 true reptiles into the two grand divisions of Shielded Reptiles 

 ( Cataphractd) and Scaly Reptiles (Squamata), but he includes the 

 Crocodilidce among the Saurians as a first grand division of them 

 Emydosauri, and the other Lizards constitute his second grand 

 division of them Lacertini. These latter are again primarily 

 divisible according to the structure of the tongue. Thus, in the 

 series of Leptoglossa, the tongue is elongate, forked, and exser- 

 tile, much as in the Ophidians ; in that of Pachyglossd the tongue 

 is short, thick, attached to the gullet, and is not exsertile ; and in 

 the Vermilingues it is Worm-like, club-shaped in front, and very 

 exsertile. 



The various genera of Saurians which have either not a trace of 

 external limbs, or have them more or less diminutive and rudi- 

 mentary either the usual two pairs or one pair only, and in the 

 latter case sometimes the fore and sometimes the hind pair being 

 deficient are included among the Leptoglossa, or the series which 

 have a forked and protrusile tongue ; and, so far as is practicable, 

 we will commence by noticing the different serpentiform genera ; 

 only, in a classification which is not confessedly superficial, it 

 will be found that the various Snake-like Saurians appertain to 

 several distinct natural families, most of the other genera belong- 

 ing to which have, in sundry cases, limbs that are well developed. 



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