PHYLOGENY OF SHELL OF TESTUDINATA 427 



bone. These plates of bone are thin, about 25 mm. long, and 

 about half as broad. On the bosses of the other scute areas no 

 such bones are found, but the summits of these bosses present 

 adequate evidence that they were once capped by similar thin 

 plates. It appears probable that some of these plates were lost 

 in the preparation of the skeleton; others may have been ab- 

 sorbed during the life of the animal. 



On the bosses situated on the neural bones and near the hinder 

 end of the vertebral scutes no thin bones distinct from the neu- 

 rals are found, but on each boss there is a rough and pitted sur- 

 face which suggests that such a bone was once there. Coming 

 now to the borders of the shell, we may examine the projecting 

 points of the peripheral bones, those points which are situated 

 at the rear of the various marginal scutes. No bones distinct 

 from the peripherals are there found, but there are indications 

 that such bones may have been present. On several of these 

 points, or bosses, are found pitted surfaces, to each of which 

 appears to have been joined by suture a bone of considerable 

 size. On the plastron of the skeleton referred to are surfaces 

 which suggest the former presence of thin superficial bones, and 

 these are situated at the center of growth of each plastral scute. 

 The one on each pectoral scute is very large and rough. If the 

 bone was once there it may have been lost during the maceration 

 of the shell. 



From the American Museum of Natural History, New York, 

 through the courtesy of its Department of Herpetology, the 

 writer has received three shells of the genus Chelys. One of 

 these, having the number 7167, is disarticulated. On this last- 

 mentioned shell the following observations have been made. 



On the fifth neural (fig. 2) there is a triangular patch of thin 

 bone which is joined to the underlying neural by suture, but 

 which in places around the edge appears to be coossified with 

 the neural. The area occupied by it is about 16 mm. long and 

 at the rear 15 mm. wide. The upper surface of this bone is 

 rough and pitted. The thin plate has the appearance of being 

 partially absorbed. The sulcus bounding the third vertebral 

 scute hes behind the area described and on the sixth neural. The 



