20G THE VOYAGE OF H.M.S. CHALLENGER. 



sesamoid bone is found ; and then is inserted into the tubercle of the scaphoid, spreading over its 

 plantar surface, and into the entocuneiform bone. A few fibrous bands end upon the proxirna 

 end of the 1st metatarsal to the inner side of the flexor brevis hallucis. In the large Phoca, 

 from beneath the inner head of the abductor hallucis, a slip from the tibialis posticus tendon 

 proceeds backwards to the inner side of the flexor brevis hallucis, and ends on the ventral or inner 

 surface of the 1st metatarsal. In Macrorhinus the tendon is inserted into the scaphoid tubercle, 

 into the entocuneiform, and the 1st metatarsal; and gives off a strong slip to the abductor hallucis. 



In Arctocefphalus gazella it is of the same size as the flexor longus hallucis. It arises from the 

 anterior fourth of the ventral border of the fibula, from the inner surface of its head, from 

 the inner surface of the tibio-fibular fusion, from the anterior three-fourths of the inner surface 

 of the tibia dorsad to the oblique line, and from the anterior fourth of the interosseous membrane. 

 About 1 inch from the ankle it forms a tendon, which goes beneath the annular ligament in the 

 groove near the ventral border of the tibia. After traversing it the tendon expands and is 

 inserted into the anterior half of the 8th tarsal or entoscaphoid bone. 1 On nearing its insertion 

 it gives off a tendinous slip (slip i.), which crosses the surface of this bone and joins the 

 plantar fascia. It also sends a strong slip over the inner or ventral half of the bone which 

 runs along the ventral plantar side of the 1st metatarsal; opposite the middle of the shaft this 

 slip divides into two (ii. and hi.). The dorsal slip (ii.) is prolonged to the distal plantar surface of 

 the 1st phalanx of the hallux. The ventral (iii.) is inserted into the distal plantar ventral side of 

 the 1st metatarsal. In Otaria it is only inserted into the scaphoid; but Murie does not 

 mention it in Trichcchus. Lucae agrees with me as to its insertion in Phoca, and Humphry 

 gives the same scaphoid and metatarsal insertions, but states "that a considerable portion 

 of its tendon extended into the ligaments under the tarsus and into the tendinous structure which 

 represents the short muscles of the hallux." In the Phocinse it is supplied by a branch of the 

 great sciatic nerve. 



The human tibia upon the posterior surface has a ridge dividing it into two ; the outer 

 division is for the origin of the tibialis posticus. In all the specimens of Seals there is no ridge, and 

 the inner surface is for the tibialis posticus. The part of the bone covered by the muscle in the 

 Phocinas is deeply scooped out, and gutter-like, the convexity being on the outer side, and in most 

 of the specimens the shaft is semitransparent. This formation gives lightness to the bones of the 

 leg but little diminution in surface. In Macrorhinus the inner surface is very slightly concave, 

 and the shaft is triangular in transverse section, the apex of the triangle giving attachment to the 

 interosseous membrane. In Arctocephcdus the inner surface is only moderately scooped in its 

 anterior third, and the shaft is triangular like the last. In all, the origin reaches the dorsal 

 tuberosity of the tibia, for the popliteal line begins at the dorsal side of the ventral tuberosity, but 

 in man the insertion of the popliteus prevents this. 



The ventral surface of the tibia is apt to be included with the inner surface, unless a number 

 of tibise are examined. The ventral border begins at the internal malleolus, runs along the shaft, 

 and terminates at the junction of the outer two-thirds and inner third of the ventral tuberosity. 

 The dorsal border runs from the external malleolus forwards to the junction of the external and 

 internal tubercles on the outer side of the bone. The space between these two borders is the 



1 See Sir W. Turner's Report, p. 50. In the Phocina? I found a sesamoid bone in the tendon of the tibialis posticus, 

 but there was none in Macrorhinus. 



