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MR. ST. G. MIVART ON THE ANATOMY OF ECHIDNA HYSTRIX. 989 
has the ulnar nerve passing along over it, and may therefore perhaps be considered to 
represent the flexor profundus. 
The various parts give origin to a very large tendon, which divides into five, sending 
off a strong division to the last phalanx of each of the five digits. Each flexor tendon, 
except that one which goes to the pollex, is held down by a strong tendinous arch or 
loop, one such arch being fixed to the distal end of each metacarpal bone, except that of 
the pollex. A similar lateral compression of the muscle exists in the Ornithorhynchus’, 
in which also there seems to be but a single flexor of the digits. 
In the Echidna, as in the Ornithorhynchus, there are one or two ossicles in the palmar 
portion of the flexor tendon.* 
Lumbricales.—I have only found four lumbrical muscles,—one pair arising between 
the flexor tendons of the index and middle digits, and going to the contiguous surfaces 
of those digits; the other pair arising between the flexor tendons of the middle and fourth 
digits, and going also to the contiguous side of those digits. 
Abductor pollicis (?).—Some muscular fibres arise from the trapezium, and are inserted 
into the radial side of the pollex. 
Interossei —'Iwo interosseous muscles arise from the palmar surface of the strong 
tendon of the flexor carpi radialis, and are inserted respectively into the outer and inner 
sides of the dorsal surface of the distal phalanx of the pollex. Two more arise from be- 
neath the base of the metacarpal of the index, and are inserted, by very delicate tendons, 
one into the inner, the other into the outer side of the dorsal surface of the distal phalanx 
of the index. | 
Another, rather larger pair arises from beneath the os magnum, and the two muscles 
are inserted by delicate tendons into the third digit, in the same way as are the two last 
deseribed into the index. Another, longer and very delicate interosseous muscle arises 
on the radial side of the continuation forwards of the tendon of the flezor carpi ulnaris, 
and is inserted into the radial side of the dorsum of the distal phalanx of the fourth digit. 
Another (the smallest of all) arises close to the proximal end of the metacarpal of the 
fourth digit, and is inserted into the ulnar side of the dorsum of the distal phalanx of the 
fourth digit. 
| Muscles of the Hind Limb. 
Psoas parvus (Plate LIII. fig. 1, ps.P).—This, which is the largest of the subvertebral 
muscles, arises, by muscular fibres, from the last three ribs, and by small tendons, or 
by tendinous fibres, from the bodies of the last three dorsal vertebree. Passing down- 
wards, it gives origin to a very strong tendon, which is inserted into the summit of the 
Meckel, loc, cit. pasha 
| Meckel, l. e. p. 28; and Owen, l. c. p. 278, and page 377. fig. 175 1. 
also exists in the Armadillos; and Professor Huxley, in his last Hunterian course (for 1865), 
"N Dasypus sexcinctus, as also the absence in that animal of any perforated flexor, and the union N VERE pee 
fundus and longus pollicis to form one tendon. This point of similarity between - Monotremes and Edentates " 
the more interesting as my friend Mr. W. K. Parker informs me he has discovered singular points of resemblance in 
the sternal structure of those two groups. 
VOL. XXY. 
As Meckel remarks, this palmar ossicle 
mentioned its existence 
2I 
