Dr. Günther does not follow Dr. Gray in arranging all true reptiles into the two grand divisions of Shielded Reptiles (_Cataphracta_) and Scaly Reptiles (_Squamata_), but he includes the _Crocodilidæ_ 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 exsertile, much as in the Ophidians; in that of _Pachyglossa_ 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 rudimentary--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 belonging to which have, in sundry cases, limbs that are well developed. Some of them, therefore, will have to be noticed as the different families to which they belong are successively treated of; and there will yet remain the curious serpentiform family of _Amphisbænidæ_, which Dr. Gray refers to his grand series of Shielded Reptiles (_Cataphracta_). The same naturalist divides the _Leptoglossa_ into two tribes, which he styles _Geissosaura_ and _Cyclosaura_; and, as constituting particular division of the former, he includes under it the family _Typhlopidæ_, which Dr. Günther refers--as we have seen--to the order of Ophidians. In the series of _Geissosaura_, the scales of the belly and (almost always) of the back and sides are quincuncial, rounded, and imbricate; the tongue is narrow, short, flat, and but slightly forked; and the head is of a conical shape, and is covered with regular shields.