MUSCLES OF THE HIND LIMB. 29 
posterior side. This muscle in Centetes is similar but with a rather more 
extensive distal insertion, while in Gymnura the insertion is nearer the proxi- 
mal end of the femur. 
The adductor magnus (Plate 4, fig. 2, m) is small. It is a thin narrow strip 
arising from the tuberosity of the ischium under the biceps, and passes to an 
insertion under cover of that of the adductor longus on the internal condyle of 
the femur. This muscle shows a less developed condition as compared with 
that of Gymnura and Centetes. The peculiar insertion into the inner head of 
the gastrocnemius described by Dobson in Potamogale, he believes is a special 
modification correlated with the animal’s habit of drawing the hind leg up 
against the tail when swimming. 
The origin of adductor quartus (Plate 4, fig. 2, &) is under cover of that of 
adductor brevis from the ventral portion of the pubis and ischium, but its pos- 
terior extent is less at the ventral margin. It increases slightly in breadth as 
it passes over the lesser trochanter to insert on the proximal third of the femur 
along the ento-posterior side of the great trochantal ridge nearly to the proximal 
insertion of the adductor brevis. In Centetes and Potamogale according to 
Dobson, this muscle presents the same relations, but it appears to be absent in 
Gymnura. 
The gastrocnemius (Plate 6, fig. 1, e; fig. 4) is a large muscle arising by two 
heads as usual. The first is from the posterior side of the external condyle of 
the humerus, by a stout tendon in which there is a small sesamoid bone; the 
second is from the internal condyle just proximal to the insertion of a portion 
of the semimembranosus to which it is joined by a few fibers. The great nerve 
trunk of the leg passes between these two heads. The insertion is as usual by 
the tendon of Achilles into the caleaneum at its posterior end. 
The soleus (Plate 6, fig. 4, @) shows an interesting relation, and one appar- 
ently not observed by Dobson in Solenodon cubanus. It arises by tendinous 
fibers from the ecto-posterior edge of the head of the fibula, and becomes fused 
with the ectal portion of the gastrocnemius above its passage into the tendon of 
Achilles. A similar condition is found in Gymnura and Potamogale, but appar- 
ently not in Centetes. 
The plantaris resembles that of Centetes in being inseparable from the gas- 
trocnemius at its origin. Its tendon is apparent, however, on the ento-lateral 
side of the gastrocnemius. In Gymnura and Potamogale the origin is described 
as distinct from that of the latter. 
The popliteus arises as usual from the thick tendon investing the ectal side 
