320 Dr. J. E. Gray on the Form of the Bones 



The bones of the sternum of a specimen of Ilomopus signatus 

 (PI. XII. fig. 1), which is \\ inch long, are very little de- 

 veloped. The front pair are very short ; the front and hind 

 lateral pairs are separated by a broad space, and form only a 

 margin to the outer side of the front and hinder lobes of the 

 sternum, the hinder pair the smallest ; the anal pair very 

 small. The gular plates are very short, band-like, and trans- 

 verse ; the postgular plates are quadrangular, diverging ; the 

 pectoral plates triangular. 



The sternum of the yoxmgKinixys erosa (fig. 2) is like that of 

 the other land-tortoises ; but the bones, except the anal pair of a 

 specimen about 2 inches long, are very narrow, only margining^ 

 the front and hind lobes. The odd bone very small. The 

 anal pair entirely covered both above and below by a hard 

 horny sheath. The front lobe with a narrow, and the sides of 

 the hind lobe with a broader (expanded) margin, the latter 

 covered above and below with the horny sheath of the plates, 

 which is thicker in these parts than usual. 



In the younger specimens of Steganopodes (or Freshwater 

 Terrapins) the front pair of bones is distinct, furnished with a 

 lanceolate odd bone on their inner edge. The front lateral 

 pair are more or less expanded, extending more or less across 

 the shell, with a dentated inner edge and more or less straight 

 hinder edge. The hinder lateral pair diverge backwards, and 

 have a more or less dilated lobe on the truncated inner edge ; 

 and the hinder pair are smaller, with a lobe on the middle or 

 towards the end of the inner edge, which is dentated on its 

 inner edge, leaving a small oval space on each side of the odd 

 bone ; a large oblong or rhombic space between the hinder end 

 of the front lateral and the front edge of the lobes of the hinder 

 lateral bone, and a more or less square cavity between the 

 hinder edge of the lobe of the hinder lateral and the lobe of the 

 hinder pair. These spaces are diminished by the increase of 

 the size of the bones ; the central one, between the processes 

 of the front and hinder lateral bones, is closed last. 



The sternal bones of the young Geoemyda spinosa (fig. 3) 

 2 inches long form only a ring round the sternum, and they 

 are very like those of Rhinoclemmys ; but the front lateral 

 bone is broader and larger, more dilated at the upper front 

 end near the odd bone, where it is divided into many narrow 

 lobes, of which a few of the lower are separated from the 

 others by a narrow space, and form a separate group. 



The sternal bones of Geoemyda grandis (fig. 4) 2£ inches 

 long (although the adult is a much larger species) are very 

 like those of G. spinosa : but the front pair are broader ; the 

 odd bone is longer and more slender, and the front lateral pair 



