OSTEOLOGY OF THE AEMOEED DINOSAXJRIA. 101 



THE GENUS STEGOSAUEUS. 



■ In a paper published in 1877 ^ Prof. O. C. Marsh proposed the genus and species 

 Stegosaurus armatus, referring it to the new order Stegosauria, which was not 

 defined. 



In 1878,^ Prof. E. D. Cope, on meager material, proposed the genus Hypsirophus 

 and briefly described the species H. discursus, and in 1879 ^ described a second 

 species, \S'. seeleyanus. Both of these species were based upon specimens from the 

 Jurassic of Colorado and later were referred by Marsh and other authorities to the 

 genus Stegosaurus. 



In 1879 * Marsh briefly described the species S. ungulatus. In 1880,^ without 

 comment, he refers to the Stegosauria as a suborder and for the first time defines 

 the genus Stegosaurus as follows: 



(1) All the bones of the skeleton are solid. 



(2) The femur is without a third trochanter. 



(3) The crest on the outer condyle of the femur, which in birds separates the 

 heads of the tibia and fibula, is rudimentary or wanting. 



(4) The tibia is firmly coossified with the proximal tarsals. 



(5) The fibula has its larger extremity below. 



Marsh briefly described the skull, brain, limbs, dermal spines, and plates. 

 Teeth were also described, but were afterwards ° discovered to pertain to the Sauro- 

 pod dmosaur Diplodocus. 



In Februaiy, 1881,' Marsh recorded additional information concerning the 

 brain, pelvic arch, and limbs. In the same communication the species S. affinis 

 was named, but inadequately defined. In a paper piiblished in May of the same 

 year ^ the following classification was proposed by him for the genus Stegosaurus: 



Suborder Stegosauria. 



Family Stegosauridse. 



Genus Stegosaurus. 



In 1882,° Marsh again raised the rank of the Stegosauria to an order and at 

 the same time defined it, placing under it two families, the Stegosauridse and the 

 Scelidosauridse. His definition is as follows: 



Order STEGOSAURIA 



Herbivorous ; feet plantigrade, ungulate; five digits in manus and pes; second row of carpals 

 unossified. Pubes projecting free in front; postpubis present. Forelimbs very small; locomotion 

 mainly on hind limbs. Vertebrae and limb bones solid. Osseous dermal armor. 



(1) Family Stegosauridse. Vertebrae biconcave. Neural canal in sacrum expanded into large 

 chamber; ischia directed backward, with sides meeting on median line. Astragalus coossified with 

 tibia; metapodials very short. 



Genera: Stegosaurus [Hypsirhoplms), Diracodon, and, in Europe, Omosaurus Owen. 



(2) Family Scelidogauridse. Astragalus not coossified with tibia; metatarsals elongated; four 

 functional digits in pes. Known forms all European. 



Genera: Scelidosaurus, Acanthopholis, Crataeomus, Hylaeosaurus, Polacanthus. 



1 Amer. Joum. Sci., vol. 14, 1877, p. 513. ' Amer. Joum. Sci., vol. 26, 18S3, p. 85. 



2 American Naturalist, vol. 12, 1878, pp. 188, 189. ' Idem, vol. 21, 1881, pp. 167-170, pis. 6-8. 



3 Idem, vol. 13, 1879, pp. 401, 402. ' Idem, vol. 21, 1881, p. 423. 



< Amer. Joum. Sci., vol. 18, 1879, p. 604. ' Idem, vol. 23, 1882, pp. 83, 84. 



5 Idem, vol. 19, 1880, pp. 251-259, pis. &-V 

 51873°— Bull. 89—14 8 



