
Othniel Charles Marsh. 15 
published nothing in this department. Two papers presented 
some Annelids considered as new, from the Jurassic of Ger- 
many. Another showed the origin of the double lobe-lines in 
Ceratites. His papers on American invertebrates comprised a 
description of a new genus of Fossil Sponge ( Brachiospongia ), 
a new form of Crustacean Trail from the Potsdam Sandstone, 
and a note on color markings in Endoceras. He also showed 
that Paleotrochis and Lignilites were not of organic origin, 
though the contrary had ‘been previously supposed. 
In the domain of Geology, his chief interests lay in the 
formations from which he secured important series of fossil 
vertebrates. Probably his greatest geological discovery was 
the Uinta Basin, an Eocene deposit of the eastern Uinta 
Mountains. It was first visited in 1870. Having studied most 
of the Tertiary lake basins in the Rocky Mountain region, he 
gave, in 1875, a synopsis of their geological features. As a 
natural result of studying Geology in Germany, he was much 
impressed with the methods of marking the separate horizons 
by means of some characteristic fossil. He believed the verte- 
brates were the most sensitive time-markers, and therefore 
endeavored to determine and limit geological horizons wholly 
by fossil vertebrate remains. The inherent fault of this sys- 
tem is that the vertebrates are not always the most highly 
differentiated and specialized types in any given fauna, and it is 
these qualities alone that can be safely employed in organic 
chronometry. This method is usually of great value in fresh- 
water deposits rich in vertebrate remains, but it can be seldom 
used to advantage in marine sediments or in formations 
containing a scanty vertebrate fauna. Thus, while the name 
Equus Beds is very appropriate for a horizon in the Pliocene, 
on account of the abundance of remains of fossil horses, the 
same cannot be said of the term Eosaurus Beds as an equivalent 
of the entire series of the Coal Measures, especially as but two 
vertebre of this animal have ever been discovered. Geolog- 
ical facts will be found scattered through many of his publica- 
tions dealing principally with fossil vertebrates. One of the 
latest problems to interest him was the age of the series of 
variegated clays extending from Martha’s Vineyard south along 
the Atlantic coast into Maryland. His investigations led him 
