Mr. Gray on the Slender-tongued Saurians. 2 75 



The former of these groups contain two very distinct sections ; the 

 one consisting of the nocturnal lizards, as the Geckoes, which are easily 

 known by the structure of their eyes and the composition of their 

 skulls ; and the other the diurnal lizards, as the Agames, Chameleons 

 of the Old World, and the Iguanas, which are confined to the new 

 continent ; the former have permanent teeth placed on the edge of 

 the jaw, while the latter have them placed on the inner side of the 

 jaw, below the edge, where they are gradually replaced by new ones 

 as their edges become worn down by use. 



As Messrs. Dumeril and Biberon have lately published a work on 

 the species of the thick-tongued lizards, leaving the description of 

 the new species which I have of that group for the present, I at once 

 proceed to the revision of the family and genera of the slender- 

 tongued kinds, and describe the various new species which have come 

 under my observation either in the National Collection or Museum of 

 the Army Medical Board at Chatham. 



The British Museum Collection of these animals is one of the rich- 

 est that I have ever had the opportunity of examining, as the novel- 

 ties of this catalogue will fully prove ; and as it is daily receiving 

 additions, I hope by the time that it is removed into its new locality 

 it will be one of the most extensive in Europe. 



Since the publication of the Synopsis of Reptiles, and my other 

 papers on these animals, I have been induced to propose a new ar- 

 rangement of them, of which the following table may be considered 

 as an outline. 



I. Typical group. Scaly Reptiles. (Squamata.) Body covered with 

 scales ; tympanic bones distinct; skull formed of separate bones. 



1. Saurians. (Saura.) Jaws united by a bony suture; legs 2 or 

 4, rarely wanting. 



Including the Saurian and Ophidosaurians of my former arrange- 

 ments, except the genera Amphisbena and Chirotes. 



2. Ophidians. (Ophidia.) Jaws very dilatile, only united by a mem- 

 brane ; legs none, or hid under the skin. 



II. Annectant groups. Shielded Reptiles. (Cataphracta.) Body 

 covered with square imbedded shields ; tympanic bones inclosed in 

 the skull, which is formed of hard united bones. 



3. Amphisbenians. (Amphisbena.) Body cylindrical, with rings of 

 square shields ; penis double. 



4. Chelonians. (Chelonia.) Body depressed, inclosed in a bony case, 

 formed of the expanded ribs and sternum ; penis simple ; legs 4 ; 

 jaws toothless. 



5. Emydosaurians. (Emydosaura.) Body depressed, elongate, in- 



T 2 



