ORDER CHELONIA. IIO9 



which is almost exclusively terrestrial, has been recorded from the 

 Continental Miocene. The Indian genus Nicoria, which is repre- 

 sented by the existing JV. (Chaibassid) tricarinata in the Siwaliks, is 

 distinguished from all the preceding forms in that the neural bones 

 have their short side placed posteriorly. The extinct Ptychogaster, of 

 the Lower Miocene (Upper Oligocene) of France, is characterised by 

 the ligamentous junction of the hypoplastral with the carapace, and 

 by the presence of a hinge between the hypo- and hyoplastrals, and 

 also by the contour of the neural and costal bones, which approxi- 

 mate to those of the true Tortoises ; from which we may assume 

 that this form was mainly of terrestrial habits. In both genera the 

 humero-pectoral sulcus cuts the entoplastral bone. 



In the land Tortoises, forming the last group of the family, the 

 neural bones are generally very short and wide, and may be either 

 hexagonal, or alternately tetragonal and octagonal ; while the costal 

 bones are generally alternately short and long at their inner and 

 outer extremities ; the suture between the marginal and costal bones 

 usually coincides with the sulcus dividing the corresponding shields, 

 and the caudal shield is generally undivided. In most cases the 

 sulcus between the humeral and pectoral shields is behind the ento- 

 plastral bone. The digits differ from those of most of the preceding 

 genera by being adapted solely for walking, and devoid of webs ; 

 while the metacarpals are shorter, and the humerus is very much 

 curved, with its radial and ulnar processes approximated. The least 

 specialised existing forms are Cynixis and Pyxis, which have neural 

 bones like those of Homopus, but costals of the ordinary Emydine 

 type ; they appear to be unknown as fossils. Hadrianus, of the 

 Upper (Bridger) Eocene of the United States, includes generalised 

 Tortoises of large size, in which the neural bones are elongated and 

 hexagonal, with the shorter lateral surfaces posterior ; the costals do 

 not alternate in length ; the vertebral shields are narrow ; and the 

 caudal shield is divided. The genus Homopus, which now includes 

 a few species of small size confined to Africa, has no ridge on the 

 palate, and the neural bones are short and hexagonal, with short 

 postero-lateral surfaces, and the caudal shield is single. It is repre- 

 sented in the Upper Miocene of Switzerland by the so-called Emys 

 scutella, and in the London Clay by E. Comptoni. In Stylemys, from 

 the White River Miocene of the United States, the short neural bones 

 have their shorter lateral surface placed anteriorly, the posterior costals 

 do not alternate in length at their extremities, and there is a single 

 caudal shield. All the remaining forms may be included in Testudo, 

 in which the palate has one or two ridges ; the neural bones usually 

 consist of an alternation of small tetragonal and larger octagonal 

 ones ; while the anterior extremity of the epiplastrals is more or 

 less thickened. In the skull the pterygoids are wide, and depressed 



