HATCHER : DIPLODOCUS (mARSH) 



9 



" The teeth of Diplodocus are cyhndrical in form and quite slender. The crowns 

 are more or less compressed transversely and are covered with thin enamel, irregu- 

 larly striated. The roots are long and slender and the pulp cavity is continued 

 nearly or quite to the crown. In the type specimen of Diplodocus there are 

 four teeth, the largest of the series, in each premaxillary, nine in each maxil- 

 lary, and ten in each dentary of the lower jaw. There are no 

 palatine teeth. 



"The jaws contain only a single row of teeth in actual use. These 

 are rapidly replaced, as they wear out or are lost, by a series of suc- 

 cessional teeth more numerous than is usual in these reptiles. Fig. 3 

 represents a transverse section through the maxillary, just behind the 

 fourth tooth. The latter is shown in place, and below it is a series of 

 five immature teeth, in various stages of development, preparing to 

 take its place. These successional teeth are lodged in a large cavity, 

 which extends through the whole dental portion of the maxillary. 

 The succession is also similar in the premaxillary teeth and in those 

 of the lower jaws." 



The Vertebrae. 



The skeleton of Diplodocus (No. 84) discovered by Dr. J. L. Wort- 

 man, in 1899, has the vertebral column especially well preserved, and 

 will be used as the basis for the following description of that part of 

 the skeleton. In this individual alone forty-one vertebrae were re- 

 covered, and they are believed to form an uninterrupted series ex- 

 tending from the axis to the twelfth caudal. This exceptionally well 

 preserved series of vertebrse was unearthed with great skill and care 

 during the season of 1899 under the immediate supervision of Dr. 

 Wortman, assisted by Messrs. W. H. Reed and A. S. Coggeshall. The 

 locality is designated as Quarry D, and is situated about one mile 

 south of Sheep Creek in the lower Sheep Creek Basin, in Albany 

 County, Wyoming. The horizon is the middle Atlantosaurus beds 

 of Marsh (the Como stage of later authors). At this locality these" beds attain a 

 thickness of perhaps 300 feet, and are underlaid by the marine Baptonodon beds 

 and are overlaid by the Dakota sandstones, with no apparent unconformities between 

 the three series. 



The surface in the immediate vicinity of the quarry is comparatively level, with 

 a gentle, northerly slope. Most of the bones of the skeleton when discovered lay on 



Fig. 3. Sec- 

 tion of maxillary 

 bone of Diplodocus 

 longus, showing 

 functional fourth 

 tooth in position 

 and five succes- 

 sional teeth in 

 dental cavity ; one 

 half natural size. 

 After Marsh. 



