148 



NATURAL SCIENCE. 



Feb., 



A Memoir on the Genus Piilaosyops and its Allies. By C. Earle. Extract 

 from Journ. Acad. Nat. Sci. Philadelphia, vol. ix., pp. 267-388, pis. x.-xiv. 



(1S92). 



We are glad to welcome as a comparatively new worker in mam- 

 malian palaeontology 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 palaeontology 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. Pala-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 oihuno-selenodont ; 

 that is to say, while the inner pair of columns formed simple cones, 



Right Upper Molar Teeth of PaliEosyops (i, 3), Limiwhyops (2), Tetmatotherium (4), pa. 

 paracone ; "ic. metacone ; /ly. protocone ; /i^'. liypocoiie ; pi. protoconule ; >»/. inetaconule. 



the outer pair were flattened and crescent-like. Molars of almost 

 identical structure occur in the European genus, Chalicotherinm. 



PalcTosyops, 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- 

 theyium, 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. 



