282 PROCEEDINGS OF THE ACADEMY OF [1887. 



ON THE STRUCTURE AND CLASSIFICATION OF THE 

 MESOZOIC MAMMALIA. 



by dr. henry f. osborn. 

 [Abstract.] 



This paper is an outline of the writer's observations upon the 

 structure of the British Mesozoic Mammals and a classification of 

 the Mesozoic Mammals in general, in view of their relationship to 

 each other and to recent orders. 



When Professor Owen completed his Memoir' in 1871 there 

 were but twenty genera of pre-Tertiary Mammals known to science. 

 Discoveries in the Mesozoic strata of Germany/ South Africa^ and 

 North America* have now increased this number to over forty gen- 

 era, five of which are from the Upper Triassic, the remainder from 

 the upper and lower Jurassic, and one from the Cretaceous.* Suc- 

 cessors of the Mesozoic mammals have been discovered at the bot- 

 tom of the American Eocene and in the lower French Eocene Beds.' 

 Among the latter are mammals which clearly connect upper Trias- 

 sic* with Quatei'nary genera.'' Through the kindness of the 

 members of the Geological Department of the British Museum I 

 was recently enabled to study the British types very carefully, and, 

 enjoying soon afterwards an examination of the fine collections of 

 Professor Marsh and Professor Cope,'" I have been able to compare 

 the type specimens of all the Mesozoic mammals, with the exception 

 of four genera." The most striking result of this comparison is the 



1. Monograph of tlie Fossil Mammalia of the Mesozoic Formations, Palaeon- 

 tographical Society, 1871. 



2. Triglyphiis, discovered by Prof. Fraas in the Rhaetic Beds near Stuttgart. 



3. Tritylodon, from the .Stormberg Beds, Upper Triassic, South Africa. 



4. Numerous genera discovered by Prof. Marsh in the Allantosaurus Beds 

 parallel with the English Purbeck. 



o. Meniscocssus, described b/ Professor Cope, from the Laramie Beds. 

 (>. I refer to Professor Cope's genera Po/ytnaslodoit, Chirox and Ptilodus. 



7. The Plagiatilax group, discovered by Dr. Lemoine at Rheims. 



8. Alicrolesles and 9 Thylacoleoz.x^\xm\.QOi by the intermediate Plagiaulacidae. 

 ](). This assistance will be more fully acknowledged elsewhere. I am es- 

 pecially indebted to Mr. Richard I.ydekker for much \alual)le assistance. 



11. Stereognathiis, Ainpkilestes, Tnglyphw;, A/ic7 olesies aittiquzis {^W^nrnget^^ 

 type specimen.) 



Full acknowledgt-ment will be made later of the use made of the valuable 

 suggestions of Professor Owen and other writers. 



