48 MEMOIRS OF THE CARNEGIE MUSEUM 
been stated this character is possessed in common by members of both these groups. 
While Cetiosaurus is an undoubted member of the Sawropoda (Opisthoccelia) as 
determined by Owen, this fact does not serve to define properly the latter term which 
remains a nomen nudum, while the Sawropoda, proposed and defined by Marsh in the 
American Journal of Science for November, 1878, page 412, should be accepted as 
the first adequately defined name for this group of dinosaurs. 
In proposing the term Sauropoda for this group of dinosaurs in the paper just 
cited Marsh adds: 
“The most marked characters of this group are as follows: 
“1. The fore and hind limbs are nearly equal in size. 
“2. The carpal and tarsal bones are distinct. 
“3. The feet are plantigrade, with five toes on each foot. 
“4. The precaudal vertebree contain large cavities, apparently pneumatic. 
“5. The neural arches are united to the centra by suture. 
“6. The sacral vertebree do not exceed four, and each supports its own transverse 
process. 
ry 
“7, The chevrons have free articular extremities. 
“8. The pubes unite in front by ventral symphysis. 
“9. The third trochanter is radimentary or wanting. 
“10. The limb bones are without medullary cavities.” 
Although the subsequent discovery of more complete material has shown that 
No. 6 of these characters is erroneous, and that certain others are possessed in common 
by some members of the Theropoda and Predentata, yet Marsh’s original definition 
still remains fairly diagnostic of the group, and the term Sawropoda should, there- 
fore, it appears to the present writer, be accepted. 
Whether this group should be considered as of only subordinal rank, as originally 
proposed by Marsh or as-of ordinal value as considered in his later publications, is a 
question concerning which there is at present no unanimity of opinion. Each 
student must, for the present at least, determine for himself the rank to be assigned 
such groups, and such decisions will necessarily be determined by, and vary accord- 
ing as certain characters are considered as of greater or less importance by the dif- 
ferent investigators. Without going into an extended discussion of this question the 
present author feels warranted in considering the Sawropoda as a distinct order, com- 
parable for instance with the Ungulata among the Eutherian Mammalia, or the Dipro- 
dontia among the Metatheria, according to Gadow’s “Classification of the Vertebrata.” 
It now remains to discuss the relations of the genus Haplocanthosawrus to the 
various genera and families of the Sauropoda that have already been proposed. 
