1120 The Amblypoda. (November, 
my return home, September Ist, after an absence of three months, 
I find that various parts of, the skeleton of Periptychus have 
reached my museum.’ On examination I find that the astragalus 
of that genus fulfills the anticipation above expressed. Jt is with- 
out trochlea, and nearly resembles that of Elephas. As it agrees 
nearly with that of Phenacodus in other respects, I only separate 
it as a family from the Phenacodontide. One other type re- 
mains to be discovered which shall connect the Periptychide 
and the hypothetical Hyodonta; and that is a taxeopod without 
a head to the astragalus—unless, indeed, the ‘ Hyodonta’ should 
prove to have such a head. I think the latter the less probable 
hypothesis, and hence retain the term Platyarthra for the hy- 
pothetical taxeopod without trochlea or head of the astrag- 
alus.” This group as at first defined had been already discovered, 
but in the above paragraph I added another definition, endeavor 
ing to preserve an apparently useless name. 
The existence of Amblypoda Hyodonta is rendered almost 
certain by the discovery that the genus Pantolestes of the We 
satch epoch is an artiodactyle with tritubercular bunodont sup 
rior molars. The ancestral type of such a form must have best 
a tritubercular bunodont amblypod. Pantolambda is such a aie 
with the tubercles modified into Vs. Moreover, such a ye: 
(Amblypoda Hyodonta) would be derived from a per iptychid Tax | 
opod with but little modification of the latter. A distinct fact 
ing of the astragalus for the cuboid bone, and probably a one 
of the carpus by an articulation of the unciform and lunar ~~ | 
would be all that would be necessary. The discovery of we : 
lambda has increased the probability of such change having% 
place in the hind foot, since the astragalus is intermediate = ei : 
between those of Coryphodon and Periptychus. This is part pee , 
seen in the form of the head, which is not separated by 4 | | 
in Periptychus, but is more prominent than in other Am ta wil | 
(Fig. 3). Thus it is possible that Amblypoda Hyodon wat 
be found to have a short head of the astragalus, ee p 
supposition above expressed. The headless astragulas ; af 
Amblypoda and of Proboscidea is perhaps a derivative © : 
not a primitive character. 
. 1 See NATURALIST for August, 1884, for figures. 
