450 The American Naturalist. [May, 
Iguanodon belongs to the group which has been called Thero- 
sauri by Fitzinger, 1843; Therosauria by Haeckel, 1866; Ortho- 
poda by Cope, 1866; Ornithopoda and Stegosauria by Marsh, 
1881; Ornithischia by Seeley, 1887. Of all these names that of 
Therosauri or Therosauria has the priority. But I do not believe 
that this name will be favored. I think it best to introduce a 
new significant name for this group of archosaurian reptiles: 
Lguanodontia,—like Crocodilia, Plesiosauria, Ichthyosauria, Aétho- 
sauria, etc., the most typical representative of this group being 
Iguanodon. To this group belong the families, Iguanodontidæ, 
Hypsilophodontidæ, Hadrosauridæ, Ornithomimidæ (?), Sceli- 
dosauridæ, Stegosauridæ, Agathaumidæ.? 
Diplodocus belongs to the group which has been called 
Opisthoceelia by Owen, 1859; Cetiosauria by Seeley, 1874; 
Sauropoda by Marsh, 1878. I think it best to use the name 
Cetiosauria introduced by Seeley, Cetiosaurus being the oldest 
member of the group, and doubtless synonymous with one and 
probably more of the American genera. Of this group there is 
evidence so far of only one family, the Cetiosauride. 
Ceratosaurus is a member of the group which has been called 
Megalosauri by Fitzinger, 1843; Harpagosauria by Haeckel, 
1866; Goniopoda by Cope, 1866; Theropoda by Marsh, 1881; 
I propose to use the name Megalosauria for this group. It is the 
oldest name used, and Megalosaurus is the oldest genus known, 
and there is no doubt that one or more of the American generte 
names will prove to be synonyms of it. ee: ; 
In this group the following families can be distinguished: 
Zanclodontide, Anchisauride, Megalosauride, Compsognathide, j 
Ceeluridz.’ ae 
_ As the result of this paper I may state this: ie 
1. The group generally called Dinosauria is an unnatural -r 
which is composed of three special groups of archosaurian wade 
etek 
* Ceratops Marsh is the same as Monoclonius Cope, as I know from actual arer ae 
the i 
study 
types. That Agathaumas Cope is the same as Triceratops Mosh wN we 
