HATCHER : DIPLODOCUS (mARSH) 5 



The Skull. 



Unfortunately there is no skull of Diplodocus in our collections."* For complete- 

 ness the figures and descriptions of the skull and lower jaw of this genus given by 

 the late Professor Marsh in his "Dinosaurs of North America" are introduced here.*^ 

 Fig. I., of the text, and Figs. 1, 2 and 3 Plate II., are after Marsh, and his description 

 accompanying these figures is as follows : 



"The skull of Diplodocus is of moderate size. Tlie posterior region is elevated 

 and narrow. The facial portion is elongate and the anterior part expanded trans- 

 versely. The nasal opening is at the apex of the cranium, which from this point 



Fig. 1. Skull of Diplodocus longus Marsh. One-sixth natural size ; seen from below ; Z>, basioccipital 

 process ; eo, exoccipital ; m, maxillary ; mp, maxillary plate ; o, occipital condyle ; p, palatine ; pm, pre- 

 maxillary ; pt, pteiygoid ; ps, parasphenoid ; g, quadrate ; t, transverse bone ; v, vomer. After Marsh. 



slopes backward from the occiput. In front of this aperture the elongate face 

 slopes gradually downward to the end of the muzzle, as shown in PI. II., Fig. 1." 



"Seen from the side the skull of Diplodocus shows five openings: a small oval 

 aperture in front, a large antorbital vacuity, the nasal aperture, the orbit, and lower 

 temporal opening. The first of these has not been seen in any other Sauropoda, the 

 large antorbital vacuity is characteristic of the Theropoda also, while the other three 

 openings are present in all the known Dinosauria. 



"On the median line, directly over the cerebral cavity of the brain, the type 

 specimen of Dipdodocus has also a fontanelle in the parietals. This, however, may 

 be an individual peculiarity. 



"The plane of the occiput is of moderate size, and forms an obtuse angle with 

 the fronto-parietal surface. 



4 The skull of Diplodocus reported in Science, Nov. 9, 1900, p. 718, when freed from the matrix proved 

 to belong to Stegosaurus. 



5 Part I., Sixteenth Annual Report, U. S. G. S., pp. 143-244, Plates 2-85, with 66 text figures. 



« References to plates and figures are altered to agree with numbers for the same in the present paper. 



