THE FAUNA OF THE ARUNDEL FORMATION OF 

 MARYLAND. 



By Charles W. Gilmore. 



Associate Curator, Division of Paleontology , United States National Museum. 



INTRODUCTION. 



The vertebrate fauna of the Arundel formation of Maryland has 

 long been a subject of interest to all workers in American Mcsozoic 

 formations. The correlation of this fauna with the Morrison (Atlan- 

 tosaurus, Como) beds fauna of the Rocky Mountain region by Prof. 

 O. C. Marsh, and the later 1 and more positive confirmation of that 

 conclusion by Dr. R. S. Lull, has been quite generally accepted as 

 the correct interpretation. The present communication gives the 

 results of a more recent study of all known specimens from the Arun- 

 del formation, and the conclusions reached are quite at variance to 

 those of my predecessors. The evidence appears to show— first, that 

 the vertebrate fauna as a whole is not to be closely correlated with 

 that of the Morrison formation of the West; second, that it contains 

 forms having undoubted Upper Cretaceous affinities; third, that it 

 consists of a combination of dinosaurian forms hitherto unknown in 

 any fauna of this continent — that is, the intermingling of Sauropo- 

 dous dinosaurs with those having Upper Cretaceous affinities. 



While the discussion of several phases of this question are neces- 

 sarily inconclusive, due to the paucity of the materials, yet the main 

 contentions, I believe, can be fully maintained. 



SOURCE OF MATERIALS. 



Practically all of the vertebrate materials known from the Arundel 

 formation of Maryland are now assembled in the United States 

 National Museum. These comprise all of the specimens collected by 

 the late J. B. Hatcher, in 1887 and 1888 for the United States Geolog- 

 ical Survey; the Goucher College collection brought together by 

 Prof. Arthur Bibbins during the years 1894, 1895, and 1896; and a 

 few single specimens that have been acquired by the United States 

 National Museum from various sources. 



1 Maryland Geol. Survey, Lower Cretaceous, 1911, pp. 173-178. 



Proceedings U. S. National Museum Vol. 59— No. 2389. 



581 



