Roy L. Moodie 459 
many forms I have examined. I know of no way to account for it save 
by paralle] development. What the causes are which have produced this 
peculiar development in these lizards is obscure. I know of nothing in 
their habits of life which could bring about such a development, since 
they are but slightly different in their mode of life from many other 
lizards which have the regular reptilian structure. 
The epiphyses are more abundant on the skeleton of Amblyrhynchus 
cristatus Gray than on any other form I have examined. There is a small 
Fie. 22. Humerus, ulna and radius of Amblyrhynchus. 1% natural size. 
one on the proximal end of each mandible, on the angular (Fig. 21), but 
none can be detected elsewhere on the skull. On the humerus of this 
form there are four epiphysial centers on the upper end and five on the 
lower (Fig. 22). The four on the upper end are of unequal size and only 
one of them is ossified. The other three are calcified cartilage. The 
ossified epiphysis occupies the head of the humerus, two small ones of 
calcified cartilage occur on the large tuberosity, and one on the lesser 
tuberosity. The five at the lower end are also of unequal size and only one 
of them is ossified. The large central bony one resembles the trochlear 
epiphysis of a mammal, but the trochlea is itself small. There are three 
39 
