344 S. W. WILLISTON 



the Wealden, and, by inference, that they are even of Middle Jurassic 

 age. Marsh consistently believed that they are equivalent to the 

 Wealden of England, which he, however, in company with other 

 good paleontologists, referred to the uppermost Jurassic rather than 

 the lowermost Cretaceous. 1 These opinions from one who justly 

 earned the distinction of being the chief paleontologic geologist 

 among the students of vertebrate fossils in America are deserving of 

 careful consideration. I must frankly say, however, that I am unable 

 to draw any such conclusions as did Mr. Hatcher. 



Cetiosaurus longns Owen is from the Great Oolite, or Middle 

 Jura; C. glymptonensis Phillips, imperfectly known, is from the same 

 horizon ; while C. brevis Owen, also imperfectly known, is from the 

 Wealden, but is referred by Seeley to Ornithopsis, by Lydekker to 

 Morosaurus. Ornithopsis Seeley is from the Wealden; O. humero- 

 cristatus Hulke, from the Kimmeridge. Other, uncertain forms are 

 from the Wealden of England. Titanosaurus is referred by Lydekker 

 to probable Upper Greensand. Remains of the Sauropoda are 

 spoken of as "frequent" in the Wealden, while from the Middle 

 Jura only a few are known, and all these are of one, or at most two, 

 species. I certainly cannot see what evidence these forms present 

 that would lead one to say that the American forms are clearly Jurassic. 

 The range of this suborder, so far as is known, is from the Middle 

 Jurassic to the Upper Cretaceous, though there may be doubt as to 

 the real age of the Indian form. Their known geographic distri- 

 bution is Europe, India, Madagascar, Africa, South and North 

 America — that is, over the whole world. The generalized characters 

 presented by them are not at all sufficiently well understood to say 

 off-hand that certain forms are older than others. No one has been 

 better acquainted with the known dinosauria than the late Professor 

 Marsh, and his opinions as to their relationships ought certainly to 

 have weight, especially as he was inclined, perhaps, to exaggerate 

 differences : 



Nearly all the American Sauropoda, indeed, show a higher degree of specializa- 

 tion than those of Europe, both in this feature [the relative length of the fore and 

 1 American Journal of Science, Vol. I (1896), p. 234; Vol. II (1896), p. 438. 

 '"I have studied the Wealden at many localities in England and on the continent, 

 and it contained a reptilian fauna similar to one I have found in the Rocky Mountains 

 and regarded as Jurassic." 



