0. U. Marsh—New Family of Dinosaurs. 167 
CLASSIFICATION. 
__ The main characters of the order Sauropoda, and of the three 
families now known to belong to it, are as: follows:- : 
Order SAUROPODA. 
late; five digits in manus and pes; 
tarsal bones unossified. Sternal bones 
in front, and united distally by cartilage ; no post-pubis. 
(1.) Family Atlantosauride. A pituitary canal. Ischia directed 
downward, with expanded extremities meeting on median 
line. Sacrum hollow. Anterior caudals with lateral 
cavities, 
(2.) Family Diplodocide. Dentition weak. Brain inclined back- 
ward. Large pituitary fossa. Two antorbital openings. 
Ischia with straight shaft, not expanded distally, directed 
lownward and backward, with ends meeting on median 
line. Caudals deeply excavated below. Chevrons with 
both anterior and posterior branches. 
(3.) F amily Morosauride. Small pituitary fossa. Ischia slen- 
er, with twisted shaft, directed backward, and sides 
meeting on median line. Anterior caudals solid. nas 
The Sa 
affinities with the Crocodilia, especially through some of the 
extinct forms. Diplodocus, for example, resembles Belodon of 
the Triassic, particularly in the large antorbital vacuities of 
the skull, the posterior position of the external nasal aperture, 
48 well asin other features. The genus Aetosaurus, from the 
same formation, is an intermediate form, and represents a dis- 
tinct order, which may be called Aelosauria. The nearer rela- 
tions of these groups will be discussed by the writer elsewhere. 
Yale College, New Haven, Jan. 21, 1884. . 
. Ceteosaurus has been fi ith a single sternal’ bone by Phillips and other 
an gcse cain hs a 
nal spe 
r of these bones, which strongly resemb 
of American Sauropoda. . 3 
