1882. ] ANATOMY OF ERETHIZON DORSATUS. 283 
The extensor carpi radialis brevior is a larger muscle, and has a 
stronger tendon, than that last noticed, which overlaps it at its 
origin. It goes to the third metacarpal. 
The extensor communis digitorum goes as usual from the external 
condyle to the four outer digits. 
The extensor carpi ulnaris takes origin from the external condyle 
and adjacent parts of the ulna, and goes to the base of the fifth 
metacarpal. 
The extensor ossis metacarpi pollicis is large and strong; it takes 
origin from the adjacent sides of the radius and ulna, but mainly 
from the ulua and the strong interosseous ligament. Its insertion is 
as usual. 
The extensor minimi digiti, arising from the external condyle, 
sends tendons to the fourth and fifth digits. 
The extensor indicis is very delicate; it takes origin from the 
middle of the exterior surface of the ulna, and sends its tendon to 
the index. 
Muscles of the Hind Limb. 
The gluteus maximus and gluteus minimus I found to be quite 
similar to those of the Agouti’. 
The gluteus medius is also as in the Agouti, save that the part of 
it which is inserted into the hinder side of the great trochanter is 
more distinct. I did not observe any distinct scansorius. 
The biceps consists of two parts, which are very similar to those 
of the Agouti: the first part arises from the sides of the first four 
caudal vertebre, and is inserted by a strong tendon into the outer 
side of the patella; the second part arises (being mainly tendinous 
at its origin) from the tuberosity of the ischium, external and 
superficial to the origin of the semimembranosus. It is inserted 
by fascia into the patella, the tuberosity of the ischium, the head of 
the fibula, and the external malleolus, and into the fascia which 
invests the outside of the leg. 
The most slender accessory muscle of the biceps, or ¢enuissimus, 
takes origin from the strong fascia which binds down the dorsal 
caudal muscles at the root of the tail, on a line with the great 
trochanter, and at the anterior end of, and covered in by, the origin 
of the first part of the biceps. It is inserted into the heel and inner 
side of the sole of the foot; in its course it lies close to the hinder 
border of the second part of the biceps; at its insertion it unites 
with the plantar fascia, having a certain adhesion to the inner side 
of the tuberosity of the os calcis, and more to the plantar surface of 
the extra tarsal ossicle. 
The semimembranosus also consists of two parts: one part, thick 
and fleshy, arises from the tuberosity of the ischium and the ramus 
below it. It goes to the upper half of the tibia (covered in by the 
1 See P. Z. 8. 1866, p. 405. What was therein taken to be the ¢ensor vagine 
FSemoris I now believe to be the sartorius. 
