148 NATURAE SCIENCE. FEB., 
A MEMOIR ON THE GENUS Palgosyops AND ITS ALLIES. By C. Earle. Extract 
from Journ. Acad. Nat. Sci. Philadelphia, vol. ix., pp. 267-388, pls. x.-xiv. 
(1892). 
WE are glad to welcome as a comparatively new worker in mam- 
malian paleontology Mr. Charles Earle, who in the finely illustrated 
memoir before us has produced a monograph which will form a fitting 
companion to those written by Professors Scott and Osborn on other 
groups of Ungulates. The systematic and methodical work now 
being undertaken by these three gentlemen on the fossil mammals 
of the United States is of the highest value and importance, since by 
this means alone can American vertebrate paleontology be rescued 
from the confusion with which it is beset through the over-zeal of 
describers anxious to procure priority for their own names. 
The group Mr. Earle has set himself to monograph is one of 
peculiar interest, since it forms part of a family of Perissodactyle 
Ungulates which has no European representatives. Pal@osyops, it 
may be observed, included animals of about the size of a tapir, with 
a skull of somewhat similar type, and the same number of digits to 
the feet. They had, however, upper molar teeth of a totally different 
type, which is described by Mr. Earle under the name of buno-selenodont ; 
that is to say, while the inner pair of columns formed simple cones, 

Right Upper Molar Teeth of Palgosyops (1, 3), Limnohyops (2), Telmatotherium (4), pa. 
paracone; me, metacone; pr. protocone; hy. hypocone; p/. protoconule; m/. metaconule. 
the outer pair were flattened and crescent-like. Molars of almost 
identical structure occur in the European genus, Chalicotherium. 
Palgosyops, together with some nearly allied forms to which 
distinct names have been applied, occurs in the upper portion of the 
Middle or Bridger Eocene; while in the Lower Bridger they were pre- 
ceded by a nearly allied but more generalised form known as Lambdo- 
therium, which was probably very close to, if not the actual ancestor 
of the group. These forms are characterised by possessing the full 
typical dentition, and by the upper premolar teeth being less complex 
than the molars, while the skull was devoid of bony horn-like appen- 
dages, and the third trochanter of the femur fully developed. Pro- 
fessor Cope regarded these forms as constituting a family by 
themselves; this view was, however, disputed by Dr. Schlosser, who 
proposed to include them in the same family with the larger forms 
from the Miocene, known as Titanotherium. 
The latter view is supported by Mr. Earle, who shows that the 
two groups can only be distinguished by the circumstance that 
Titanotherium and its allies have at least some of the upper premolars 
as complex as the molars. In the gigantic Titanotherium of the 
Miocene, the skull was provided with enormous bony horn-like 
1 In the one named species of Lambdotherium, the first lower premolar is absent. 
