REPORT ON THE SEALS. 207 



ventral surface. The popliteal line, which begins about the middle of the shaft in all, runs 

 forwards and ends at the dorsal side of the ventral tuberosity. A casual look at the bones might 

 suggest that the concave surface giving origin to the tibialis posticus is the inner surface, but such 

 is not the case. The small triangular surface for the popliteus also belongs to the inner surface. 

 This is best seen in Macrorhinus, where the popliteal surface advances upon the inner to a greater 

 extent than in the rest. In Arctoccphalus the inner surface is more convex, and the popliteal line 

 stands out like a ridge ; this is still more evident in the Phocinas. The popliteal line in the Seals 

 only gives origin to the flexor longus digitorum. 



In the Phochife and Macrorhinus, where the pes is always in line with the trunk, it will 

 in the backward and forward motion of the paddle, assist in bringing the pes to the middle 

 line, i.e., adduct it, and turn the sole a little upwards, i.e., pronate it. In Arctoccphalus in 

 walking it will extend the ankle, raise the inner side of the pes and the heel, besides giving the 

 other movements when swimming. 



Pes. — The Outer Region in all the specimens has one muscle, the extensor brevis 

 digitorum. 



The Extensor brevis digitorum in the Phocinaj arises from the outer surface of the os calcis, 

 ventral to the peroneal tendons, from the superior dorsal border of the os calcis, and slightly from 

 the surface below the latter. It forms three muscular slips which end in two small tendons, the 

 common extensor of the first running backwards between them. The ventral slip goes between the 

 1st and 2nd metatarsal bones, and is inserted into the ventral side of the proximal end of the 

 1st phalanx of the 1st digit. The dorsal slip goes between the heads of the 4th and 5th metatarsals, 

 and is inserted into the proximal end of the 1st phalanx of the 3rd digit. 



In Macrorhinios leoninns it is in two separate slips. The dorsal slip arises from the os calcis 

 ventral to the peronei, and passes between the 1st and 2nd metatarsals, and is inserted into the 

 proximal end of the ventral side of the 1st phalanx of the 2nd digit, and, by a small tendon from 

 the side of this one, into the distal dorsal side of the 1st metatarsal. The ventral slip arises from 

 the astragalus on its outer surface, and from the outer surfaces of the scaphoid and external cunei- 

 form bones. The tendon passes back to the interval between the 4th and 5th metatarsals, and is 

 inserted into the proximal dorsal side of the 4th digit. 



In Arctoccphalus gazclla it is in two parts. The dorsal part has two heads of origin. The 

 larger head arises from the dorsal surface of the os calcis and from the dorsal surface of the cuboid. 

 The smaller head arises from the same bones, but to the ventral side of the large head. These two 

 heads unite and are inserted into the proximal end of the 1st phalanx of the 2nd digit. The second 

 part arises from the adjacent sides of the os calcis and astragalus, and from the cuboid, and is 

 inserted into the proximal end of the 1st phalanx of the 3rd digit. 



The Inner or Plantar Region has adductors, flexores breves of the phalanges, and abductors. 

 In Macrorhinus the inner head of the flexor of the hallux and the abductor hallucis were the only 

 two intrinsic muscles seen ; the rest had evidently decomposed. 



The Adductors. — In Phoca vitulina the adductor minimi digiti is found. In Arctoccphalus 

 there are the adductor hallucis, the adductor minimi digiti, and the adductor ossis metatarsi primi. 



The Adductor minimi digiti in Phoca vitulina arises between the bases of the 3rd and 4th 



