Prof. 0. C. Marsh on the Dinosauria. 79 



XI. — Classification of the D in osa u ria . 

 By Prof. O. C. Marsh*. 



In the ]\Tay number of tlie ' American Journal of Science ' 

 (p. 423), I presented an outline of a classification of the 

 Jurassic Dinosaurian reptiles of this country which I had 

 personally examined. The series then investigated is depo- 

 sited in the museum of Yale College, and consists of several 

 hundred individuals, many of them well preserved, and repre- 

 senting numerous genera and species. To ascertain how far 

 the classification proposed would apply to the material gathered 

 from wider fields, I have since examined various Dinosaurian 

 remains from other formations of this country, and likewise, 

 during the past summer, have visited most of the museums 

 of Europe that contain important specimens of this group. 

 Although the investigation is not yet complete, I have thought 

 the result already attained of sufficient interest to present to 

 the Academy at this time. 



In previous classifications, which were based upon very 

 limited material compared with what is now available, the 

 Dinosaurs were very generally regarded as an order. Various 

 characters were assigned to the group by Von Meyer, who 

 applied to it the term Pachypoda ; by Owen, who subsequently 

 gave the name Dinosauria, now in general use ; and also by 

 Huxley, who more recently proposed the name Ornithoscelida, 

 and who first appreciated the great importance of the group, 

 and the close relation it bears to birds. The researches of 

 Leidy and Cope in this country, and of Hulke, Seeley, and 

 others in Europe, have likewise added much to our knowledge 

 of the subject. 



An examination of any considerable portion of the Dino- 

 saurian remains now known will make it evident to any one 

 familiar with reptiles, recent or extinct, that this group should 

 be regarded, not as an order, but as a subclass ; and this rank is 

 given to it in the present communication. The great number 

 of subordinate divisions in the group, and the remarkable 

 diversity among those already discovered, indicate that many 

 new forms will yet be found. Even among those now known 

 there is a much greater difference in size and in osseous 

 structure than in any other subclass of vertebrates, with tlie 

 single exception of the placental JMammals. Compared with 

 the Marsu})ials, living and extinct, the Dinosauria show an 

 equal diversity of structure, and variations in size from by 



* Communicated by the Author, having been read before the National 

 Academy of Sciences, at the Philadelphia meeting, November 14, 1881. 



