Roy L. Moodie 463 
mals, but we now know that they are present in very generalized reptiles. 
When we come to know the primitive Reptilia better the meaning of the 
epiphysial structures will be more clearly understood. It is evident that 
epiphyses are of various origins. Some arise undoubtedly through use, 
some represent atrophied elements, and some appear to arise from other 
causes. I am of the opinion that the epiphyses of the Lacertilia are 
inherited structures which they have obtained from their Rhynchocepha- 
lian ancestors and the fact that the arrangement of these structures in the 
lizards and mammals is the same cannot, it seems to me, be due to like 
causes. ‘There is some real fundamental cause for such an arrangement. 
Why epiphyses develop in some forms and not in others is another question 
and can have no bearing on this suggestion. 
Broom (12) has recently called attention to the arrangement of the 
epiphyses in the human hand and foot where they occur at the base of 
all of the phalanges, and at the distal end of the metacarpals and meta- 
tarsals of digits II, III, IV and V, but at the proximal end of the first 
metacarpal and metatarsal. He suggests that possibly the first metacarpal 
and metatarsal have gone into the wrist and ankle and cites for compari- 
son the manus of Oudenodon, where the first digit is not reduced. This 
suggestion as to the fate of the first element of the first digit of the hand 
and foot is by no means a new one, since the same opinion was held by 
many of the older anatomists, but it is of interest here because of the 
bearing it has on the arrangement of the epiphyses, which we should 
expect to find in the primitive Theriodontia and Therocephalia. If speci- 
mens of these animals are ever found well enough preserved to show the 
epiphyses we should expect to find the arrangement exactly as it is in 
some lizards. ‘There should be no epiphyses on the proximal end of the 
metacarpals and metatarsals, but they should be present on the distal end 
and on the proximal end of the phalanges. 
It is to be noted from the foregoing discussion of the epiphyses of the 
lizards that a great many of them are of calcified cartilage. The presence 
of an abundance of calcified cartilage in the skeleton appears to be char- 
acteristic of the Squamata excepting, perhaps, the snakes. Dr. Williston 
tells me that there are always abundant evidences of calcified cartilage in 
the fossilized skeletons of the mosasaurs. In the ear region, on the girdle 
bones, on the vertebre and, whenever preserved, the sternum and the 
sternal ribs, are entirely of calcified cartilage, as are also the tracheal 
rings. According to the same authority, this condition is never found in 
the plesiosaurs. There is not the slightest trace of calcified cartilage on 
the skeleton of these animals. 
