74 FieLp Co_tumpian MustumM—GeEovocy, Vot, II. 
ferentiated, nor are there any muscular markings. On the posterior 
border, near where the ulnar rugosity should be, there are the open- 
ings of two large canals, one on either side of the margin (4 and ¢ of 
the figures). On what seems to be the ventral surface, near the 
front border of the bone: and nearly opposite the other openings, 
there is a large one with its mouth, as in the others, directed distally. 
On the dorsal surface, and near the middle transversely, there is a 
fourth opening, much smaller than the others. All of these canals 
unite near the center of the bone in a rounded cavity or ampulla, as 
shown in Figs.3 and 4. In Pl. XXIII, Fig. 1, a large opening is seen 
on the posterior border below a rugose space, and another opening 
is seen towards the front leading into a groove. This was apparently 
a canal leading into a groove on the opposite side of the bone in the 
uninjured specimen, with another opening corresponding to the fora- 
men which lead into a groove shown in the photograph on the 
exposed surface of the bone. The bone was, however, injured before 
I studied it, as is indicated by the restored border in the figure. 
The posterior opening probably corresponds to the united é and ¢ of 
the other figures. In Fig. 2 of this plate is also seen a foramen on 
the posterior margin of the bone (the left one of the figure). All 
these three bones are probably humeri. Figs. 4 and 5 of the plate do 
not show these canals; from their shape they are probably femora. 
In Fig. 1, Pl. XXII, there is seen at the lower margin a groove 
(e), partly converted into a canal, which probably corresponds to one 
or the other of the grooves of Fig. 1, Pl.. XXIII. I believe this 
groove corresponds to the ectepicondylar groove or foramen of the 
chelonia, lacertilia, Belodon, Champsosaurus, and some of the notho- 
saurs andichthyosaurs. 1 may add that a similar groove is sometimes. 
indicated in the humerus of the mosasaurs, as shown in Pl. XLIV, 
Vol. IV of the University Geological Survey of Kansas. Why these 
canals and grooves should disappear in the adult humerus is not 
apparent; they are doubtless for the ‘passage of vessels. The 
ampulla at the junction of the four canals in the embryonic bone is 
between the apices of two conical ‘‘epiphyses,” the larger epiphysis 
occupying the chief part of the distal portion of the bone, the smaller 
one the proximal. The fractured specimen discloses these epiphyses 
with a smooth rounded surface, as shown in Pl. XXII, Fig. 3, 
the outer part peeling away as does the bark from a tree. 
This ephiphysial-like method of ossification has been compared 
with a somewhat similar structure in the Chelonians as an evidence of 
relationship between the two orders of reptiles. 
——s ae ed 
——— oe 
