DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 455 
above-described peroneus quartus; finally they both lose themselves in the expanded 
tendon or fascia at the root of the fourth metatarsal, common to them and the outer 
portion of the extensor brevis digitorum. 
Diagram of the flexor-tendons of the left hind foot. 
Pf. A small portion of the superficial plantar fascia 
left attached to the plantaris (Pla), which is car- 
ried into the sole of the foot, MJ.d. Flexor 
longus digitorum, tendon near the heel. Fl. 
Flexor longus hallucis, as it joins the previous 
tendinous expansion. /.b.d. Flexor brevis digi- 
torum. JZ. Lumbricales to the great and little 
toe. =». Indicating the position of the uniting 
tendon, equivalent to an accessorius. 
vee apt & 
The plantaris on reaching the sole of the foot (woodcut, fig. 7, P/a) presents a 
structural difference from the condition found in Otaria. The change consists chiefly 
in a greater expansion of its plantar fascia and in a less development of fleshy fibres. 
From the fascia in question four broad and strong tendons are derived, as is the case in 
the forms compared; but in the Walrus these are inserted into the distal ends of the 
proximal phalanges, Three or four weak muscular slips (*, woodcut, fig. 7) are mingled 
and considerably interwoven with the ligamentous structure; and as they are attached 
to its deep surface they consequently are almost entirely hidden, whereas in Otaria they 
show as long and moderately strong fusiform bellies. 
There is no accessorius muscle ; but a distinct short tendinous slip passes between the 
outer border and deeper surface of the plantaris and the superficial surface of the flexor 
longus digitorum. The arrow (=—) in woodcut, fig. 7, points to its position, otherwise 
hidden by the plantar fascia. 
The flexor brevis digitorum (woodcut, fig. 7, F.4.d) agrees with those of the Eared 
Seal, excepting that the fifth belly sends off a fascia of insertion both to the fourth and 
fifth digits on their adjoining sides. 
Abductor hallucis (woodcut, fig. 8, Ab.h).—The presence of a muscle answering to 
one of these in the foot of the Walrus, manifests a commencing change in the adapta- 
tion of the pes as an instrument of clutch as well as of support. The muscle in 
question has a long narrow belly arising by a tendon from the extra bone outside the 
