452 Reptilian Epiphyses 
Our main interest in these propodials is the fact that the cones of 
osseous matter (Fig. 11) described above have frequently been called 
epiphyses. But when these plesiosaurian structures are compared with 
the true epiphyses of other animals, they are found to be widely different. 
Epiphyses are always at the ends of the long bones and never go to form 
any part of the shaft. These cones in the plesiosaurs form part of the 
diaphysis of the propodial, and are to be eompared to the similar 
—_= SS = 
=—— 
——— 
Ria. 14. Mire. 5: 
Fic. 14. A section through thesbone figured in “10” showing the spiral 
arrangement of the bone fibers. 1 1/10 natural size. 
Fic. 15. Section through the femur of an adult turtle, Trionyx. The 
endochondral bone A is clearly distinct from the perichondral bone B. 1% 
natural size. 
structures found in the limb bones of the turtles, lizards and crocodiles 
(Figs. 15, 16 and 17). The peripheral portion of the plesiosaur bone 
which is called the shaft by Lydekker, is the periosteal ossification, and 
goes to form a portion only of the diaphysis. The cones which Lydekker 
calls epiphyses are the endochondral bone evident in all embryos of the 
