HOLLAND: THE OSTEOLOGY OF DIPLODOCUS MARSH DAT 
THE SKULL. 
MATERIALS UPON WHICH OUR KNOWLEDGE OF THE SKULL oF DipLovocus Is BASED. 
At the time when Mr. Hatcher published his first paper upon Diplodocus he 
made use of the words, ‘‘ Unfortunately there is no skull of Diplodocus in our col- 
lections.” He therefore repeated the figures and descriptions of Professor Marsh in 
order to make his account of the animal complete, so far as possible. One of the 
specimens secured for the Museum by Mr. W. H. Utterback, in Wyoming, in the 
year 1902 (Acc. 8%"), yields the entire posterior portion of a skull in very perfect 
state of preservation. While the anterior portion of this skull and the lower jaws 
are missing, the specimen, which has been very carefully and skillfully freed from 
the matrix, throws a great deal of light upon the structure of the posterior portion 
of the skull. Both Mr. Hatcher and the writer were accorded by the authorities of 
the United States National Museum the fullest opportunity to examine and mi- 
nutely study the two skulls upon which Professor Marsh based his description in his 
work upon the Dinosaurs of North America. (See Plates XXIII.-V.) These skulls 
were designated by Professor Marsh as specimen 1921 (U.S. N. M., No. 2672), and 
specimen 1922 (U.S. N. M., No. 2673). <A cast of the latter, which is the more 
perfect specimen, was made with the consent of the officers of the United States 
National Museum. One half only of the external surface of this skull is thor- 
oughly freed from the matrix. Using this half as the basis of our work, we re- 
stored the other half, using the portion of the skull belonging to the Carnegie Mu- 
seum in modeling the occipital region. The skull employed in the restoration in 
the British Museum embodies in its outline the well-ascertained characteristics of 
these two skulls. Through the kindness of Professor Henry Fairfield Osborn we 
were enabled to secure for study a cast of the reproduction of the skull of a Diplo- 
docus recently made by Mr. Hermann at the American Museum of Natural His- 
tory. (See Plate XXVI.) This skull (A. M. N. H., No. 969) is based upon a speci- 
men, somewhat fragmentary in character, obtained by the American Museum of 
Natural History, but it serves to illustrate some of the more important features of 
the structure under discussion. Mr. Hermann, so far as the external portions of 
the upper part of the skull are concerned, was unfortunately compelled to rely 
largely upon the figures and descriptions given by Professor Marsh, and in a few 
minor respects has not been quite successful in interpreting them. ‘The restoration, 
though valuable, is defective, as was the original. In addition to the material 
mentioned above, which was at the command of the writer at the time the repro- 
duction of the skull was prepared, there are in the possession of the American Mu- 
