HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS 49 
This will be the more easily understood if we first notice briefly the principal char- 
acters of the different families within that order. 
Marsh has divided the Sauropoda into six families which he has named as fol- 
lows: (1) Atlantosawride ; (2) Diplodocide ; (3) Morosawride ; (4) Plewrocelide ; (5) 
Titanosauride ; (6) Cardiodontide. 
As already stated in my memoir on Diplodocus, when discussing the taxonomy 
of that genus, it is not improbable that the number of families recognized by Marsh 
is too great and should be somewhat reduced. However it would seem premature 
to attempt a revision of the genera and families of this group until the large and 
splendid collections recently brought together by the Carnegie Museum, the Ameri- 
can Museum and the Field Columbian Museum have been thoroughly studied. It 
is safe to say, however, that no such reduction in the number of families as that 
proposed in the second yolume of the English edition of Zittel’s ‘“‘ Text-Book of 
Paleontology ” will become necessary. Nor will it be found necessary or desirable 
to associate in the same family genera so different as are Brontosuwrus and Moro- 
saurus as was done in the volume just cited. 
From the foregoing description of the types of Haplocanthosawrus priscus and 
H. utterbacki it will readily appear that the affinities of that genus are with the 
Morosawride. The relationships with that family are shown by the expanded 
superior extremity of the scapula; the general form of the different pelvic elements, 
more especially the pubes and ischia; the simpler structure of the presacral verte- 
bree ; the short spines of the dorsals and sacrals; the biconcave centra of the cau- 
dals and in the relative breadth and height of the sacrum. While the relationships 
with the Morosawridx are clearly indicated by the presence of these and other char- 
acters of scarcely less importance, yet there are present certain characters even more 
marked than most of those which at present serve to distinguish even the most 
widely separated families of the Sawropoda now known. ‘These are the perfectly 
simple neural spines of the anterior dorsals and posterior cervicals; the different 
position in the sacrum of the sacrals with codssified sacral spines; the greater num- 
ber of dorsal vertebree and the much simpler structure of the individual vertebree 
throughout the entire vertebral column. Such differences as these will doubtless be 
considered by some as of family or at least subfamily importance. Since, for the 
most part at least, they are only such differences as we might reasonably expect to 
find among the more primitive and less highly specialized members of that family 
I prefer to regard Haplocanthosaurus as pertaining to the Morosawride and including 
species the most generalized of any yet known in that or any other family of the 
Sauropoda. 
