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, biit 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 interossei 

 (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, ah). 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 \^ertebrae to the 

 fascia investing the til^ia (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 counteipart 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 \-ertel)rae. 

 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 he liut 

 little doubt that Fewkes is correct, but it is further probable that the cutaneous 

 muscle (dermo-flexor 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 latissirnus dorsi. 



