CHELONIA. 785 



The outline of all the original bones and their processes can be detected in 

 the bony plates, so that it would appear that growth commencing in the parts 

 indicated in the young extends gradually in all dnections, till at last this secondary 

 osseous structure embraces aU the constituent bones, leaving only their articular 

 processes free, the bones themselves preserving their outlines. 



Variation, however, is not confined to the plastral plates, but occurs also in the 

 shells, independently of differences ascribable to age. In youth, the shell is of a 

 more rounded form than in after life, when it is a more elongated oval. In some 

 specimens the anterior margin of the shell and the anterior vertebral swelhno- 

 are fuller than in others ; the vertebral Hue is raised in a few, while in others it is 

 rounded off at the sides. 



In fresh healthy specimens, the upper shell is always entirely covered with 

 skin so thick as to obscure the granular surface under it, but in adults it sometimes 

 becomes abraded, exposing the almost white granular shell below it. 



These curious mud turtles when left to themselves will slowly and cautiously 

 extend their necks, but as soon as they are approached they do not attempt to 

 escape, but withdraw with great rapidity into their shells and firmly close them. I 

 have never observed them snap at objects, in the same way as Trionyx, and the 

 much more formidable Chitra, which darts out its long neck with a rapidity un- 

 paralleled among animal motions. 



When the head is retracted it is completely hidden so that the anterior margins 

 of the carapace and sternum meet. The skin on the long retracted neck forms 

 two folds ; the innermost but highest fold is so formed that its upper border, which 

 is slightly longer than the snout, and so, doubtless for the protection of that sensitive 

 part, overhangs it ; but at the sides of the mouth it slopes downwards and back- 

 wards, the free margin in that position of the fold lying along the chin, so that by 

 this arrangement the mouth is not covered by this fold. The most external fold 

 which is formed by the skin at the base of the neck, covers the whole of the inner 

 fold against which it lies, and aU that part of the mouth left uncovered by it, leav- 

 ing ooly the nostrils unprotected. 



The neck when retracted is so doubled on itself, that the base of the cervical 

 vertebrse, at the anterior extremity of the carapace, is on the same line with the 

 tip of the snout, the posterior bend being opposite the inguinal notch of the 

 sternum, and pushing backwards before it the coils of the intestines which par- 

 tially embrace it on either side. 



This, like the other members of the genus, frequents muddy bottoms, and, when 

 jheels dry, it buries itself in the mud, at no great depth below the surface. 



The female in laying her eggs, which are round and about an inch in dia- 

 meter, scrapes a shallow hole for them in the mud and then covers them up. 



They are exclusively vegetable and grain-feeders. 



This species appears to be generally distributed throughout Burma, extending 

 along the various rivers that debouch into the main stream, from Lower Pegu up 

 to Bham6, where I obtained examples, and it doubtless ranges still higher. 



c 5 



