276 ZAGLOSSUS. 
arise at the base of the third metacarpal and pass one to its radial and one to 
its ulnar side, inserting on the first phalanx. From a similar origin in the fascia 
covering the carpals at the base of the fourth metacarpal a small muscle passes 
to the investing tissue on the radial side of metacarpal 4, but there is no corre- 
sponding muscle on the ulnar side, unless, as seems quite probable, this is repre- 
sented by a small muscle passing to the radial side of the fifth digit, that takes 
origin from a cartilaginous pad running from the pisiform bone to the base of 
digit 4. These five small muscles are doubtless to be considered the interosser 
(Plate 1, fig. 3). 
A seventh small muscle arises just distal to the pisiform bone in the an- 
terior prolongation of the tendon of flexor carpi ulnaris, and passes to the radial 
side of digit 5, into the terminal phalanx of which it inserts. This muscle 
seems to correspond to an abductor digiti quinti (Plate 1, fig. 3, ab). This last 
muscle apparently is not present in the Echidna, as it was not found by Mivart, 
Fewkes, or Westling. It is possible that it has been retained in the Proechidna 
to counterbalance the loss of the tendon from the profundus, as otherwise the 
fifth digit would be unprovided with a special flexor. The interossei of the 
Proechidna seem to be essentially as in the Echidna. 
MUSCLES OF THE HIND LEG. Concerning the homology of the glutei 
(Plate 1, fig. 1, gm, gme) in the Echidna, there has been more or less disagree- 
ment, and their relations in the Proechidna are quite similar. That portion 
of the panniculus muscle from the spines of the coccygeal vertebrae to the 
fascia investing the tibia (named by Fewkes the dermo-flexor cruris) was con- 
sidered by Mivart a gluteus maximus. This muscle is also present in the Pro- 
echidna, as well as a second muscle just anterior, whose counterpart is found 
in the Echidna. In the former animal this second muscle is a broad sheet arising 
by thin aponeurosis from the third and fourth sacral and first caudal vertebrae. 
It tapers to an insertion by a flat tendon at the middle of the femur along the 
distal end of the trochanteric ridge. This muscle Mivart is inclined to consider 
a gluteus medius.and Westling follows this determination. Fewkes doubts 
Mivart’s interpretation, and would call this muscle a gluteus maximus, at the 
same time giving a new name to the superficial muscle to which Mivart had 
assigned the term maximus. From its origin and insertion there can be but 
little doubt that Fewkes is correct, but it is further probable that the cutaneous 
muscle (dermo-flecor cruris) may be a derivative of the gluteus maximus, as 
indeed Mivart suggested. The two divisions therefore would be analogous 
to the cutaneous and brachial portions of the latisstmus dorsi. 
