SCALED REPTILES. 395 



of a longitudinal ridge on the palatal surface of the fore part of the lower 

 jaw. Nearly allied to Trionyx are the general Pelochelys and Chitra, each 

 represented by a single species from the Oriental countries. In the former 

 which extends from India to the Malayan Islands the eyes have a more for- 

 ward position than in the type genus, this feature being still more marked in 

 the gigantic Indian Cfiitra, where they are situated close up to the snout, the 

 whole skull being very long 

 and narrow. The foregoing 

 genera constitute a sub-family 

 by themselves ; and a second 

 group of equivalent value is 

 formed by the other three 

 genera. The two essential 

 characteristics of the second 

 group are to be found in the 

 presence of a skinny flap be- 

 neath the under shell behind 



which the hind-foot can be Fig. 10. A SOFT TOUTOISE. 



withdrawn and the complete 



union of the hyoplastral and hypoplastral elements of the lower shell. Exter- 

 nally the shell is distinguished by the pustular form of the sculpture. Of the 

 three types of the sub-family, the Indian Emyda is specially distinguished by 

 possessing a series of marginal bones round the hinder portion of the 

 carapace. There are but three species, and in the largest of these the shell 

 does not grow to more than about ten inches in length. Of the two African 

 genera, the one known as Cycloderma has a complete scries of neural bones 

 running down the middle of the carapace ; whereas, in the nearly related 

 Cyclanorbis the series is incomplete, so that some of the costal bones of 

 opposite sides come into contact with one another in the middle line. 



It may be added that in the absence of any connection between the bones 

 of the pelvis and the lower shell, as well as in the mode of articulation 

 between the upper and lower jaws, and the notch in the ring round the 

 aperture of the ear, the soft-tortoises resemble the Cryptodira. In certain 

 forms an'd certain structural features of the skull they are, however, more like 

 the Pleurodira. 



ORDER III. SQUAMATA. 



SCALED REPTILES. 



By far the largest of all the four orders of existing reptiles is the one including 

 the lizards, chameleons, and snakes ; each of those groups forming a sub-order 

 by itself. And here it may be remarked how unimportant is the external 

 form of reptiles in regard to their zoological affinities. The New Zealand 

 tuatera, for instance, which externally is like a lizard, has nothing whatever 

 to do with the Squamata, but forms an order by itself ; whereas ordinary 

 lizards and serpents are comprised in one and the same order. Moreover, the 

 blindworms, which in external appearance are like snakes, form a portion of 

 the sub-order typified by the lizards. A general, but by no means invariable, 

 feature of the Squamata is the covering of overlapping horny scales on the 



