EEPOET ON THE SEALS. 195 



The Extensor proprius hallucis in the Phocinae and Macrorhinus lies along the dorsal side of the 

 extensor communis digitorum, under cover of the peroneus longus. It arises from the whole of the 

 ventral surface of the fibula, from a very slight margin of the outer surface of the interosseous mem- 

 brane next the shaft, and from the ventral border of the shaft from the termination of the outer 

 border to the junction of the middle and posterior thirds. It crosses from the dorsal side of the 

 extensor communis to its ventral side, runs beneath the annular ligament between the tibialis anticus 

 and the extensor communis digitorum, and goes over the tendon of the tibialis anticus to the 

 ventral surface of the tarsus, then it ascends gradually to the outer surface of the distal end of the 

 1st metatarsal. It is inserted into the distal tibial outer surface of the same, into the proximal end 

 of the 1st phalanx, and into the capsule of the joint between. In the PhoeinEe it is supplied by 

 the musculo-cutaneous nerve (ventral division). 



In Arctocephalus gazella it is almost as large as the tibialis anticus in the same animal. It arises 

 from the anterior two-thirds of the ventral surface of the fibula, from the anterior half of the dorsal 

 border of the tibia, from a small triangular surface of the tibia posterior to its head, and between 

 its short outer border and its dorsal border, from the fusion of the tibio-fibular articulation beneath 

 the origin of the extensor longus digitorum, and from the interosseous membrane. It courses back- 

 wards between the tibialis anticus on its ventral side and the extensor longus digitorum on its 

 dorsal ; beneath the annular ligament it forms a tendon, which passes over the tibio-fibular joint 

 and the tarsus, and runs along the dorsal side of the 1st metatarsal. It is inserted, after the 

 expansion of its tendon, into the proximal end of the outer surface of the 1st phalanx. In Otaria 

 it arises from the fibula and interosseous membrane, and to the proximal end of the proximal 

 phalanx of the hallux. In the PhocinEe and Macrorhinus it extends the digit, and then flexes the 

 ankle, and depresses and abducts the pes. In Arctoceplwlus it only extends and flexes. 



The Extensor communis or longus digitorum, named by Lucae the extensor quatuor digitorum, in 

 the Phocina? and Macrorhinus is an elongated triangle situated between the tibialis anticus and the 

 peroneus longus. The latter partially overlaps it on the dorsal side, and it partially overlaps the 

 tibiabs anticus, and crosses the extensor hallucis. It arises from the triangular surface of the tibia 

 posterior to the superior tuberosity, marked off inferiorly by a faint ridge, i.e., the short outer border 

 which extends from the middle of the outer surface of the superior tuberosity backwards and 

 upwards to the dorsal border of the tibia, from the tibia anterior to the fusion of the bones of the 

 leg, from the capsule of the joint, and from the outer surface of the tibia and fibula where they 

 fuse posterior to the origin of the peroneus longus. It forms a strong tendon, which passes back- 

 wards, crosses over the extensor hallucis, and goes beneath the annular ligament dorsal to the 

 extensor hallucis at the posterior tibio-fibular articulation. Having traversed this, it crosses the 

 ankle-joint and enters the groove on the middle of the outer side of the tarsus, which terminates 

 over the proximal end of the 3rd metatarsal bone. Here it expands and divides into four tendons. 

 The first or ventral passes obhquely over the ventral distal end of the 3rd metatarsal and expands 

 upon the upper proximal end of the 1st phalanx of the 2nd digit. The second tendon passes back 

 over the middle of the outer surface of the 3rd metatarsal, and expands upon it. The third crosses 

 obbquely over the middle of the dorsal side of the 3rd metatarsal, goes backwards upon the ventral 

 side of the 4th metatarsal, and expands upon the proximal end of the inferior side of the 1st 

 phalanx. The fourth crosses obliquely backwards and upwards from the proximal dorsal end of the 

 3rd metatarsal, over the middle of the outer surface of the 4th metatarsal, and reaches the ventral 



