72 MEMOIRS OF THE CARNEGIE MUSEUM 
number of genera, species and individuals in the Wealden they are almost entirely 
replaced by the Predentata and 'Theropoda. And the Iguanodontia so abundant in 
the latter formation are quite unknown in the former. The same dissimilarity 
though in a less striking degree is noticeable when the fauna of the Purbeck is com- 
pared with that of the Atlantosawrus beds, and it is not until we get down into the 
middle of the Odlite that we find a dinosaurian fuana comparable even with that of 
the upper and middle Atlantosawrus beds. 
In consideration of the evidences mentioned above it appears to the present 
writer that the dinosaurian fauna of the Atlantosauwrus beds, as we now know it is 
unmistakably Jurassic in type, but that these beds may in their uppermost mem- 
bers represent a portion at least of the lower Cretaceous. 
CarNEGIE Museum, April 15, 1903. 
ADDITIONAL REMARKS ON DIPLODOCUS. 
By J. B. HarcuHer. 
Since publishing my memoir! on the osteology of Diplodocus additional discoy- 
eries have thrown more light on the structure of these strange reptiles. It thus 
becomes necessary to make certain alterations in the description and restoration then 
given, especially relating to the structure of the fore limbs and feet. As stated in 
the text of my memoir there were at that time in the collections of this museum 
no representatives of the fore limbs or feet of Diplodocus and the brief descriptions 
of those elements there given was based entirely upon the published descriptions by 
Professor Osborn and upon photographs of the limbs kindly loaned by him. For- 
tunate discoveries of the fore limbs and feet of Brontosawrus (No. 563) by Mr. C. 
W. Gilmore and of the greater portion of a skeleton of Diplodocus (No. 662) by 
Mr. W. H. Utterback have demonstrated two important errors in my previous paper. 
These are : 
First—The radial articulation at the distal end of the humerus is on the in- 
ternal side and anterior to the internal portion of the ulnar articulation instead of 
being external and anterior to the latter as stated in my memoir. When in position 
the proximal end of the ulna entirely enclosed that of the radius posteriorly and 
' Memoirs Carnegie Museum, Vol. I., No. 1, pp. 1-68, Pl. 1-13. 
