1909. | ANATOMY OF CERTAIN UNGULATA, Wat 
origin. In addition to these three heads there is a fourth, which 
is obviously referable to the triceps complex. Its origin is from 
the lower half of the humerus and its situation is posterior to and 
between that of the last two heads mentioned. It is divisible 
into two parallel muscles, which join before their fleshy insertion 
on to the olecranon to the external side of the rest of the triceps. 
Antilocapra has only three extensor muscles the tendons of 
which are inserted upon the phalanges of the toes, or rather four, 
of which two become united at the wrist, and may therefore be 
regarded asa single muscle. In the middle of the metacarpus only 
three tendons can be seen. Messrs. Windle & Parsons describe 
as long extensor muscles in the Ungulata the tendons of which are 
inserted upon the phalanges: (1) Extensor communis digitorum ; 
(2) Extensor minimi digiti; (3) Extensor profundus digitorum, 
which, however, is described as only occurring in the Elephant 
and occasionally in Suidee. 
The four muscles in Antilocapra have the following origins and 
insertions :— 
(1), (2). Two muscles arise one below (not deep of) the other, 
and in close contiguity at their origin from the external condyle ; 
the lower head, which is the smaller, also varies, and perhaps 
may be said to chiefly arise from the shaft of the ulna quite at 
the commencement of the latter. The two tendons are perfectly 
distinct until a little way beyond the wrist, when they absolutely 
jom. These two muscles together form, as I presume, the 
extensor minime digit (or extensor digitorum lateralis). 
(3). A thin muscle, arising from the external condyle under 
cover of the upper part of the extensor minimi digiti, is reinforced 
by a long slender muscular slip from the ulna, and ends in a 
tendon which closely accompanies that of the next muscle to be 
described. The tendon runs between the two toes covered by 
the intrinsic extensors of the hand and supplies both digits. 
This tendon with its two branches contrasts with the broad 
flattened termination of the tendon of the extensor minimi 
and of the next muscle to be described. The division of the 
tendon into two is quite low down, in fact at the very end of the 
cannon-bone. I imagine that this muscle is the extensor com- 
munis digitorwn. 
4). The third (see above), or perhaps fourth, long extensor 
muscle of the hand of Antilocapra arises higher up the humerus, 
below and in contact with the thick fleshy extensor carpi radialis. 
Its tendon, which has been already referred to, supplies the 
medius digit. It has no second head that I could discover. 
I suppose that this muscle is the equivalent of the eatensor 
profundus digitorum, which has been stated in the case of the 
Pig to be inserted upon the index and medius digits *, 
I now pass on to the muscles visible on the extensor side of the 
forearm before considering the arrangement of the flexors. 
* Hide Windle & Parsons. 
Proc. Zoou. Soc.—1909, No. XII. 12 
