ART. 18 ON A NEW SKELETON OF DIPLODOCUS GILMORE / 



Ornithiscliia : 



Camptosaurus mcdius Marsh. 



Dryosaurus altus Marsh. 



Laosaurus gracilis Marsh. 



Stegosaurus sp. 

 Ci'ocodilomorphi : 



GoniophoUs sp. 

 Chelonia : 



Glyptops utahensis Gilmore. 

 Phytosauromorphi : 



Hoplosuchus Jcdyi Gilmore. 



That this preliminary list will be greatly augmented by the study 

 of material already in hand, there is no doubt. 



THE SPECIES OF DIPLODOCUS 



Four species of Diplodocus have been proposed. Named in chron- 

 ological order these are: Diplodocus longus Marsh, D. lacustrls 

 Marsh, D. carnegrii Hatcher, and D. hayi Holland. 



Diplodocus longus^ the genotype, was established in 1878 ^ on 

 caudal vertebrae from the midcaudal region. Hatcher ^ has shown 

 that a hind limb and foot mentioned in the original description per- 

 tain to the genus Apatosaurus {Bi'ontosaurus) and can therefore no 

 longer be considered diagnostic of Diplodocus. The type specimen is 

 from the Morrison formation near Canon City, Colo. 



In 1884 Marsh * described D. lacustrls from the same formation 

 near Morrison, Colo. In the original description a maxillary, teeth, 

 and lower jaws only are mentioned. This was distinguished from 

 D. longus by its smaller size and " the much more slender jaws." 



In 1901 Hatcher ^ added a third species, D. camegii, based on a 

 well-preserved skeleton, lacking the skull, from Sheep Creek, Albany 

 County, Wyo. 



In 1924 Dr. W. J. Holland ^ described D. hayi based on the pos- 

 terior part of a cranium from Wyoming, chiefly distinguished by 

 the absence of a pineal fontanelle in the parietal. 



This brief review of the specimens upon which the four species 

 of Diplodocus were based shows at once the impossibility of properly 

 contrasting their essential specific differences, and the specific identi- 

 fication of the National Museum specimen is therefore rendered diffi- 

 cult, if not impossible, until there has been a thorough revision of 

 the genus. 



2 Marsh, O. C, Amer. Journ. Sci., vol. 16, p. 414, 1878. 



3 Hatcher. J. B., Mem. Carnegie Mus., vol. 1, p. 55, 1901. 

 * Marsh, O. C, Amer. Journ. Scl., vol. 27, p. 166, 1884. 

 ^Hatcher, J. B., Mem. Carnegie Mus., vol. 1, p. 57, 1901. 



« Holland, W. J., Mem. Carnegie Mus., vol. 9, p. 399, 1924. 



