296 J. L. Wortman — Cope's Tertiary Vertebrata. 



by one hundred and thirty-three beautiful lithographic plates. 

 As it covers but little more than one-half of the entire Ter- 

 tiary fauna, it is soon to be followed by another volume of 

 equal dimensions which will be devoted to the later horizons. 



To students of Mammalogy, this work will prove of unusual 

 interest on account of the flood of light which it throws upon 

 the origin and relationship of many groups which have hith- 

 erto proven puzzles to the best zoologists. One of the leading 

 questions in the study of the Mammalia is their origin and 

 succession. It is well known that they make their first appear- 

 ance in rocks of Triassic age; that they continue to be repre- 

 sented by a few small marsupial-like creatures up to the begin- 

 ning of the Cretaceous period, where, with a single exception,* 

 the record is lost until the Eocene is reached. Tt is likewise 

 well-known that the fauna of this period is comparatively 

 highly specialized and comes into existence, so far as we now 

 know, without announcement in the preceding formation. 



Previous to the discoveries of Professor Cope, the Wasatch 

 was the -oldest Eocene deposit of which we had any knowl- 

 edge. These beds contain the remains of an extensive fauna, 

 a large proportion of which is composed of Perissodactyle 

 ungulates. They likewise contain Kodents, Lemurs, Creodonts, 

 Taxeopods, etc. 



In the present volume we have brought to our attention an 

 Eocene fauna which antedates that of the Wasatch, viz : that 

 of the Puerco. Here, so far, no Perissodactyles have been dis- 

 covered ; neither have Eodents as yet been found, although it 

 appears to be quite rich both in species and individuals. Since 

 these groups have always been hitherto regardedas a constant 

 feature of any early Eocene fauna, this is somewhat remark- 

 able. 



The Perissodactyles appear to be replaced by a most extra- 

 ordinary* group to which an ordinal rank has been assigned by 

 the author under the name Taxeopoda. The Rodents are repre- 

 sented by the Tceniodonta, an assemblage of extinct forms with 

 large scalpriform incisors in both jaws, while Lemurs, Creo- 

 donts and primitive allies of the Coryphodonts go to make up 

 the list of the mammals. 



Altogether, the fades of this fauna is much more primitive 

 than that of any other group of Eocene Mammalia so far 

 known, and its discovery may be justly regarded as the most 

 important that has been made in this subject within the past 

 decade. To those who await with confidence the discovery of 

 the connecting links between the mammals of the Jurassic and 



* Messrs. Wortman and Hill discovered the remains of a small Stereognath mar- 

 supial in the Laramie deposits of Dakota in the summer of 1883, associated with 

 the bones of huge Dinosaurs. To this species Cope gave the name Meniscoessus. 



