Miscellaneous. 77 
Astragalus with two truncate or concave distal arti- 
cular facets for the cuboid and navicular bones ; 
no epicondylar foramen of humerus.......... Diplarthra. 
The Condylarthra have as yet been only found in the lowest horizon 
of the Eocene period, the Puerco and Wasatch, and only on the 
North-American continent. Appropriately to this position in time, 
its structure indicates that it is the most primitive type of the order 
of the Perissodactyla. A number of genera and species belong to 
it; and these fall into two families, which are defined as below. 
They conform to the definition of the order in possessing an alter- 
nating arrangement of the carpal bones and a third trochanter of 
the femur. The approximation to the Hyracoidea is greater than 
that of any group of the Perissodactyla. That order agrees with 
the Condylarthra in the simple articular extremity of the astragalus, 
which, however, is less convex; but it has a very peculiar articu- 
lation with the anterior face of the distal extremity of the fibula, 
seen in no other group of Ungulates. In the manus the lunar bone 
is very peculiar, not being divided below into two facets as in other 
Ungulates, and articulating with the carpals of the trapezoides series 
(the intercalare) as well as with the unciform. In these points the 
Condylarthra agree with other Perissodactyla. In Hyrax there is 
also no epicondylar foramen. The two families are defined as 
follows :— 
Dentition bunodont; toes 5—5; premolar teeth 
different from the molars above and below .. Phenacodontide. 
Dentition lophodont, with crescents and deep val- 
leys; premolars partly like molars below; 
PROC SN MPP cas tp arcins eee okt Ad Leet cdane of the Meniscotheriide. 
The bunodont dentition and five toes on all the feet give the 
Phenacodontide the lowest place in the suborder and order as the 
most generalized type known. The Meniscotheriide have a quite 
specialized dentition ; and until I learned its condylarthrous charac- 
ter I was at a loss to account for the presence of such perfection in 
so old a type. The number of the toes is yet unknown; but I sus- 
pect, from the large size of those I have seen, that they are less 
numerous than in the Phenacodontide. It appears to have had no 
descendants, and is a good illustration of Dr. Kowalewsky’s views as 
to the persistence of the “adaptive ” over the ‘“‘ non-adaptive ” types 
of articulation. Kowalewsky observed that the types of Ungulata 
which have the carpo-metacarpal and tarso-metatarsal articulations - 
simple, and not alternating, have become extinct. In those which 
persisted the metapodials articulate with two bones of the carpal 
or tarsal series. The same rule has generally applied in the Ungu- 
lates to the distal astragalar articulation. The Diplarthra and 
Amblypoda with the double articulation have left descendants, while 
the Condylarthra with the single articulation have disappeared 
without leaving a trace. Tho Proboscidea, which have the same 
“oe, 
