1873.] ALVEOLAR SURFACES OF TORTOISES. 727 



Pyxis arachnoides, Gray, Cat., App. p. 14. (Plate LX. fig. 7, 

 alveolar processes of jaws.) 



Section IV. Alveolar surface of the upper jaw narrow, slightly 

 concave on the sides of the lower jaw, very narrow, linear, 

 with a slightly raised edge on each side, and a very slight 

 longitudinal ridge across the front. The lower jaw slender 

 and, weak. Hinder part of the dorsal disk separated from 

 the front and central part by an irregular transverse cartila- 

 ginous suture. Sternum undivided. 



Tribe VII. Kinixyina. 

 1. Kinixys. 

 Skull rather elongate. Forehead flat. Orbits oblong, longitu- 

 dinal. Nose- hole square, with a prominence in the centre of the 

 upper and lower margins. Intermaxillary rather high. Front edge 

 of upper jaw even. Alveolar surface of upper jaw narrow, rather 

 wider behind, with a very slight indication of a thickening on the 

 hinder part of the inner edge ; centre slightly concave in front, and 

 becoming much more concave as it proceeds between the inner nos- 

 trils. The groove behind the inner nostrils rather wider in the 

 middle behind. Lower jaw weak, slender, rounded in front ; the 

 alveolar surface narrow, linear the whole of its length, and with very 

 narrow acute edges. 



■'o*- 



Kinixys erosa, Gray, Cat., App. p. 16. (Plate LX. fig. 8, al- 

 veolar processes of jaws.) 



This order of Tortoises may be thus arranged : — 



I. The dorsal disk solid. 



t The sternum solid. 



A. The alveolar surface of the upper and lower jaw with two 



ridges, one on each side extending nearly the whole length. 



a. The centre of the alveolar surface of the upper jaw with a lon- 



gitudinal ridge. Xerobates. 



b. The centre of the upper alveolar margin concave, subcircular. 

 The hinder ridge of the alveolar process of the lower jaw nearly 



united in front. Elephantopus, Megalochelys, and Aste- 

 rochelys. 

 The hinder ridge of the lower jaw separated by a broad space 

 in front. 

 Anal margin of plates separate. 



Pectoral plates reaching the centre of the sternum. Che- 

 lonoides. 

 Anal margin of plates united together. 



Pectoral plates broad, reaching the centre of the sternum. 



Scapia. 

 Pectoral plates narrow, not reaching the centre of the 

 sternum. Manouria. 



