98 PROCEEDINGS OF THE ACADEMY OF [1883. 



cannot be used to distinguish a subclass, or in some instances an 

 order. In like manner, the definitions of his orders and suborders 

 embrace many characters whicli are not usually regarded as 

 defining groups higher than families. Such, e. g.^ are the numbers 

 of toes ; relative sizes of fore- and hind-limbs ; solidity or non- 

 solidity of bones ; presence or absence of dermal armor. Much 

 light was, however, thrown on the subject by Professor Marsh, b}' 

 the numerous characters he brought to light, and the number of 

 forms he defined. 



The constitution of the pelvis is shown by Marsh to differ 

 materially in the different members of the Dinosau7-ia, As this 

 region presents characters diagnostic of the order Dinosauria 

 itself, its modifications within the order become of importance. 

 The ungulate or unguiculate character of the feet must also not 

 be neglected, although of less importance than in the mammalia. 

 If the order is susceptible of division into suborders, it must be 

 by means of the following definitions, which I select from Marsh's 

 diagnoses : 

 Feet ungulate ; pubes projecting and connected in front ; no 



postpubes ; Opisthocoela . 



Feet ungulate ; pubes projecting free in front ; postpubes present ; 



Orthopoda. 

 Feet unguiculate; pubes projecting downwards and coossified dis- 



tally ; calcaneum not produced ; Goniopoda. 



Feet unguiculate; calcaneum much produced backwards ; ? pelvis; 



Hallop)oda. 



I have used for these orders the oldest names when the defini- 

 tions first given were not erroneous, although they were inadequate. 

 Thus I think the name Opisthocoela (Owen') must take precedence 

 of Sauropoda Marsh. I combine Marsh's two divisions, Stego- 

 sauria and Ornithopoda^ into one, and use the name I gave in 

 1866 and redefined in 1869,^ for the division thus remodeled. 

 The name Goniopoda^ given at the same time, I designed to 

 embrace the carnivorous Dinosauria^ but included in my defini- 

 tion some characters which are of less significance than I then 

 attached to them. 



Prof. Huxley recognized thx*ee families ; the Scelidosauridae and 



» PalaBontology, 18G0, p. 273. 



^ Transactions American Philos, See, xiv, p. 90. See American Naturalist, 

 1883, March. 



