794 The Condylarthra. [August, 
to the middle carpal and tarsal articulations. The orders with 
the double articulation continued, while the Condylarthra, with the 
single articulation, have disappeared, leaving only modifed de- 
scendants. The Proboscidea, which have the same simple distal 
_ articulation of the astragalus, still remain, however, to show an 
exception to the generalization. They have, however, an alterna- 
tion in the second series of the posterior foot not present in the 
Taxeopoda. The relations of the genera of these three families 
are as follows : 
PERIPTYCHIDÆ. 
In Periptychus only are the posterior feet known. The carpus 
is yet unknown. The successional generic modifications are seen in 
FIG. 2.—Periptychus rhabdodon Cope, jaws represented in fig. 1 seen in profile; 
koth natural size. From the Puerco beds. Original. 
the addition of cusps to the inner sides of the premolars aan both 
jaws, and to the true molars of the upper jaws. In pee 
we have the largest number of dental cusps and lobes, pis 
Periptychus the next. In Anisonchus the inferior premolars 
their inner ledges, and the true molars their anterior i pe 
lobes. The molars are still further reduced in Hemithlæus, 
the premolars in Haploconus. 
The characters of the genera are the following : 
I. Three pr 
Fourth apio hiaai like molars; inferior premolars without internal get 
and 
anterior 
II. Superior molars with intermediate tubercles, and tubercles 
posterior to the internal cusp; four premolars. 
