226 The American Naturalist. [March, 
proach three feet in length. Besides the turtles, Oreodon frag- 
ments are scattered about. Among the several fine skulls of 
these animals that we found was one that was entirely perfect 
and had attached to it some four or five of the cervical verte- 
bre. On the levels below the three- to four-foot bed of sand- 
stone the scattered remains of that strange looking ungulate, 
Menodus are frequently met with. Careful search will usu- 
ally reveal an exposed piece that, when carefully followed 
with pick and chisels, will prove to be an invaluable speci- 
men. During our short stay in the region a perfect lower jaw 
of Menodus was found. It was lying upside down with only 
one angle exposed. The rest was buried in the lumps of clay, 
which, from their hardness and tendency to slip upon one 
another, made digging very difficult. But by dint of much 
work with chisels, much paste, glue, many strips of cloth and 
paper, and much more patience, the jaw was finally freed and 
turned over. It was a fine specimen, all the teeth were pres- 
ent and perfect, and it was not noticably distorted. In none 
of the large museums of the east has the author seen a speci- 
men as perfect. The pasted and glued jaw was left in the field 
that night which, to our anxiety, brought with it a thunder 
storm. We feared that we should see no more of specimen, 
or, that it would be totally ruined. Storms severe enough to 
be cloud-bursts are not unheard of in the region and when 
they break on the ridge they sweep with terrific force down 
the gullies and cafions, carrying everything before them to 
the valley below. Such storms explain the great amount 
of erosion that has been done, for in none of the cafions, save 
those that run far back into the ridge and have a growth of 
trees, can there be found a running stream of water that ever 
reaches Hat Creek. In some of the larger Bad-land ravines 
a small stream of water may be found, but such streams are 
usually swallowed up, leaving a perfectly dry bed before they 
reach the open plain or have run very far in it. Most of the 
ravines are completely dry. But the cloud-bursts would carry 
off the loose, friable, sun-baked earth on the surface of the 
walls, exposing the indurated age beneath to be burnt and 
cracked in its turn. 
