102 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



In 1884 ' this classification was republished, without change except in the 

 definition of the order the additional character "cervical ribs free" was inserted. 



In 1887 ^ the discovery of additional specimens enabled Marsh to contribute 

 further to the knowledge of the skull and dermal armor. In the same paper 

 the tliree new species Stegosaurus stenops, S. sulcatus, and S. duplex were briefly 

 designated. The close relationship of tie Stegosauria with the Ornithopoda was 

 recognized and a list of important characters wherein they differ was given. 



The first restoration of Stegosaurus was published by Prof. Marsh in 1891 ^ 

 and additional characters relating to the osteological structure and life appearance 

 of the animal were noted. 



In 1893 '' Lydekker republished Marsh's restoration of Stegosaurus and inad- 

 vertently referred it to the genus HypsiropTiUs. Later in the same publication 

 (p. 438), Marsh calls attention to this error. 



In 1895 ^ Marsh published a revised definition of the Stegosauria, here again 

 called a suborder. With a few emendations these definitions were repeated in 

 1896 ° in his Dinosam's of North America. 



In 1900 ^ Lydekker referred the two British species Omosaurus aimatus and 0. 

 hastiger to the genus Stegosaurus quite oblivious of the fact that the genus already 

 contained an American species S. armatus. Lucas in 1901 ° described the species 

 8. marshi and in the foUomng year it was referred by him to the new genus Hop- 

 Utosaurus,^ and in the same article the generic name Dacentrurus was proposed 

 for Owen's genus Omosaurus, preoccupied. 



In the same year Lucas ^° contributed further to oiu" knowledge of Stegosaurus, 

 particularly as to the life appearance of the animal, presenting a restoration by 

 Charles E. Knight. 



In 1902 " Hay created the superfamily Stegosauridea and under the genus 

 Stegosaurus the following species were recognized: S. affinis, S. armatus, S. discursus, 

 S. duplex, S. seeleyanus, S. stenops, S. sulcatus, and S. ungulatus. 



In that year Lucas '^ announced for the first time the "probable" alternating 

 arrangement of the dermal plates of opposite rows. 



Zittel " defined the genus Stegosaurus thus : 



Skull narrow and depressed, relatively very small, and brain cavity in proportion to size of the 

 body more dimiaiitive than in any other land vertebrate. Orbits small; laterally directed; supra- 

 temporal vacuities small and rounded; nasals nearly half as long as the slcull. Mandibular ramus deep, 

 pierced by a lateral foramen. Teeth very numerous, bluntly pointed, more or less spatulate in form, 

 loosely socketed in a single functional series. Vertebrae slightly amphicoelous or with flat ends, the 

 cervicals with short ribs and dorsals with much elevated neural arches, on which the stout dorsal ribs 



1 Nature, vol. 31, 1884, p. 68. 



2 Amer. Journ. Sci., ser. 3, vol. 34, 1887, pp. 413^17, pis. 6-11. 



3 Idem, ser. 3, vol. 42, 1891, pp. 179-181 with pi. 9; also Geol. Mag., ser. 3, vol. 8, 1891, pp. 385-387, pi. 10. 

 < Nature, vol. 48, 1893, p. 304, fig. 3. 



5 Amer. Journ. Sci., ser. 3, vol. 50, 1895, pp. 496-497. 

 8 leth Aim. Rept. U. S. Geol. Surv., pt. 1, 1894-95. 

 ' Cat. of Fossil Reptiles and Amphibia, vol. 4, 1900, p. 252. 



8 Proc. U. S. Nat. Mus., vol. 23, 1901, pp. 591,692, pis. 23,24. 



9 Science, vol. 16, 1902, p. 435. 



10 Animals of the Past, 1901, pp. 106, 107, fig. 24. 



" Bull. 179, U. S. Geol. Survey, 1902, pp. 495, 496. 



" Animals before Man in North America, 1902, p. 171. 



13 Text-book Paleontology, English Translation, vol. 2, 1902, pp. 241, 242. 



