322 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Dinosauria. Teeth buds have been discovered in the embryos 

 of Trionyx and Chelone by Rose\ but the presence or absence 

 of teeth in the turtles, unless of a particular type, would be 

 of no classificatory value. Teeth have been aborted for so long 

 in the Chelonia that their form cannot be determined from the 

 embryonic vestiges. 



The "conical epiphyses" which have been referred to as 

 present in turtles and plesiosaurs are not epiphyses at all, 

 but are endochondral cones such as are found in all the groups 

 of the Sauropsida, and they are represented by cartilaginous 

 cones in the Amphibia. The term "epiphyses" was first ap- 

 plied to these structures by Seeley,*^ who used the term inad- 

 vertently, I believe, and did not at all intend to convey the 

 idea that there were present in the turtles and plesiosaurs 

 "characteristically mammalian elements."' That these struc- 

 tures are not epiphyses is well shown by the condition found in 



Fig. 1. 



the limb bones of certain lizards. In the humerus of the 

 Galapagos lizard, Am.hlyrhynchus, for example, there are pres- 

 ent three sets of structures. These are the peri- and endochon- 

 dral tissues and the terminal bony epiphyses, which differ from 

 the mammalian epiphyses in that they are in part formed of 

 calcified cartilage. Epiphyses are always situated at the ends 

 of bones and never penetrate the shaft to any extent. The so- 

 called epiphyses in turtles and plesiosaurs penetrate the 

 cylindrical shaft and almost meet in the center. These struc- 

 tures persist throughout the life of the individual, of the plesio- 

 saurs at least, but in the turtles they are not so persistent. In 

 some forms of the Chelonia the endochondral cones are re- 

 placed by cancellated bone. The manner of development of the 

 cones and perichondral cylinder is well shown in figure 1. 

 The fibers of bone are densest near the middle of the shaft 

 and splay out near the ends of the bone. The endochondral 



5. Rose, Carl, 1892, Anat. Anz., Bd. YII, p. 748. 



6. Seeley, 1887, Phil. Trans., p. 191. 



7. Osborn, 1903, Mem. Am. Miis. Nat. Ilist, vol. I, pt. VIII, p. 465. 



