458 Reptilan Epiphyses 
ulna. At this stage there are none apparent on the metacarpals or 
phalanges. There is a distinct center at each end of the femur, tibia and 
fibula, but none on the metatarsals or phalanges. In the adult of the 
same species, 135 mm. in length, the epiphyses are fully as distinct as 
they are in the young, with the exception of that at the head of the 
humerus, which appears to be partly fused with the shaft. In the adult 
form there are epiphyses in the hand and foot. 
In the adult specimen of Heloderma suspectum Cope, the epiphyses 
are abundant and in places quite mammalian in appearance. The upper 
end of the humerus has a small oval epiphysis in the center with a smaller 
one on each tuberosity. That at the distal extremity of the humerus is 
quite broad and has a particularly mammalian aspect, being quite long 
from side to side, entirely covering the lower end of the bone. It is 
divided into three condyles by two trochlear grooves. The epiphysis at 
the upper end of the ulna is quite ike a mammalian olecranon. The one 
Fig. 21. The left mandible of Amblyrhynchus. The shaded part # repre- 
sents the epiphysis. A= Angular. 1% natural size. 
at the lower end is dise shaped. The radius has small, poorly developed, 
calcified epiphyses at each end. In the hand the metacarpals have epiphy- 
ses at each end and they are present at the base of all of the phalanges 
(Fig. 19). On the upper and lower end of the femur there are epiphyses, 
the lower one having a mammalian aspect. The tibia has a small epiphy- 
sis on each end and the same condition holds for the fibula. On the 
tibiale there are two small ones and one also on the fibulare. In the foot, 
as in the hand, there are epiphysial structures on each end of the metatar- 
sals, with the exception of the first, and one at the base of all of the 
phalanges (Fig. 20). I have not been able to detect epiphyses on the 
girdle bones of this form, although Dollo has reported them on some of 
the forms examined by him. Siebenrock has seen epiphyses on the ilia of 
Uroplates. : 
There are in many of the epiphyses of Heloderma certain resemblances 
to similarly placed structures of the mammals. This is very remarkable 
as being the only case in which there is such a resemblance among the 
