182 The American Geologist. March i890. 
horn-cores growing from the frontal bones strongly recall the head of 
the ox. In most skulls the fore maxillary bones occupy the front 
place, but here Prof. Marsh describes one anterior to those, which he 
calls the "rostral" bone. A corresponding bone in front of the 
symphysis of the lower maxillaries is called the "dentary" bone. It 
is not quite clear from Prof. Marsh's paper whether or not these 
bones exhibit the true osseous tissue. He calls them dermal ossifica- 
tions and says that they were covered by strong horny beaks like 
those of birds. In addition to these extravagances of nature in this 
singular genus of reptiles, the hinder part of the head is covered with 
enormously expanded parietal and squamosal bones all four of which 
meet the frontals and are bordered behind and outwardly by a row of 
small ossicles, "epoccipital bones," like tubercles or blunt spines 
which, says Prof. Marsh, had horny coverings and in old animals were 
coossified with the adjoining plates. 
Prof. Marsh adds that these stray fossils characterize a distinct 
horizon in the so-called Laramie group of the Upper Cretaceous, which 
may be traced for 800 miles along the Rocky mountains. 
Mr. Ho worth contributes a paper to the same journal on the question, 
"Did the great Siberian rivers flow southward in the Mammoth age?" 
He shows that the whole area of northern Asia has long been slowly 
rising and thus tending toward' a state of things that prevailed in the 
past. He shows that no great amount of elevation would be necessary 
to prevent the northern flow of the Obi and the Yenessei, their upper 
reaches being now only 200 or 300 feet above the sea, so that an eleva- 
tion of from 40 to 50 fathoms would suffice to reverse the drainage of 
this region. 
The structure of the Asiatic continent requires as a corollary from 
this conclusion that a vast Mediterranean sea must have existed there, 
and of this Mr. Howorth offers the following evidence : 
1. The scattered lakes over this part of Asia are inhabited by the 
same animals. 
2. The intervening stretches of desert contain semi-fossil shells of 
the species still living in the lakes. 
As a further argument Mr. Howorth points out that it has been a 
difficulty with geologists to understand how the great sea which once 
certaiidy filled the Aralo-Caspian depression was supplied with water. 
This difficulty he removes by the theory advanced in his paper. 
Mr. Howorth further remarks that the great rivers of European 
Russia still flow southward and that what he here maintains regard- 
ing the Obi and the Yenessei was also true of the Lena. It concludes 
by calling attention to the influence which such a change in the phys- 
ical geography must have had on the climate by rendering it milder 
and more capable of supporting the fauna whose remains are now 
found in the Tundras of Siberia. 
It is an obvious inference from Mr. Howorth's premises that north- 
ern Asia is rapidly tending back to the former state and that in an ag 
