REPORT ON THE SEALS. 209 



In Arctocephalus the outer muscle is the same as in Phoca ; the inner arises from the tendon of 

 the tibialis posticus, which is attached to the outer side of the anterior end of the entocuneiform 

 bone, and from the anterior outer half of the same, and is inserted as in Phoca. 



The flexores breves in Otaria consist of one single and four double muscles ; as also in Trichechus 

 (Cunningham). While Professor Cunningham alludes to no differences in their insertions, Dr. 

 Murie gives the insertion in Otaria of the first interosseus into the fascia covering the metacarpo- 

 phalangeal joint of the hallux, which is very like what I have stated. Excluding Phoca, we agree 

 as to some change in the tibial side of the 2nd metatarsal. Murie in Otaria derives the tibial head 

 of the 2nd muscle from the proximal ends of the 1st and 2nd metacarpals. The smaller moiety 

 of this muscle, that next the hallux, has also a partial origin or attachment to the superficial layer 

 of the interosseous fibres and hallucial metacarpal. Professor Cunningham, in describing the flexor 

 brevis indicis, gives the origin of the tibial head from the base of the 1st metatarsal. In my 

 account of this digit in Arctocephalus I describe an adductor from the anterior tibial third of the 

 2nd metatarsal. 



Tlic Abductors. — In Phoca vitulina these are the abductor hallucis, the abductor minimi digiti, 

 and the abductor tertius quinti digiti. 



In Arctocephalus the abductor hallucis, the abductor minimi digiti, the abductor tertius quinti 

 digiti, the abductor ossis metatarsi quinti, and the abductor ossis metatarsi primi are found. In 

 Macrorhinus the abductor hallucis only is described. 



The Abductor hallucis in Otaria is named the flexor brevis hallucis, in Trichechus (Murie) the 

 abductor hallucis, and in Trichechus (Cunningham) the inner head of the flexor brevis hallucis. 

 In Phoca vitulina it originates by three separate slips, which are close to each other and attached 

 posteriorly. The outermost arises from the scaphoid bone upon the tendon of insertion of the 

 tibialis posticus, a little to the outer side of the inner head of the flexor brevis hallucis, which lies 

 at a greater depth in the sole, and from the adjacent posterior surface of the os calcis ; the middle 

 from the tendon of the tibialis posticus before it reaches the scaphoid just anterior to its insertion ; 

 the inner by a slip which comes from the outer posterior side of the sesamoid bone of the tibialis 

 posticus tendon. These three slips unite a little posterior to the sesamoid bone, forming a strong 

 tendon, which is inserted into the inner distal plantar side of the 1st metatarsal. On both sides of 

 the slip which comes from the tibialis posticus tendon, and on the outermost side of the middle 

 two-thirds of the outermost tendon, there are a few muscular fibres. 



In Macrorhinus it arises, in common with the inner head of the flexor brevis hallucis, from the 

 outer posterior half of the scaphoid bone upon the tendon of insertion of the tibialis posticus before 

 it reaches the scaphoid. It is a strong fibrous band which is directed backwards ; midway 

 between its origin and insertion, it is joined on the outer side by the outer head, and the two 

 together are inserted into the proximal tibial plantar surface of the 1st metatarsal. 



In Arctocephalus it arises from the tubercle on the posterior end of the sesamoid bone of the 

 tibialis posticus, and is closely united with its tendon. It courses backwards along the tibial side of 

 the 1st metatarsal, and is inserted into the distal tibial side of the 1st metatarsal and the proximal 

 end of its 1st phalanx, receiving some fibres from the tibialis posticus, which pass over the 

 sesamoid bone into it. Its almost tendinous nature, its close association with the tendon of the 

 posticus, and its arising from the sesamoid bone, show that it has a similar function to the posticus. 



In Otaria Murie does not describe this muscle. 



(ZOOL. CHALL. EXP. — PART LXVIII. — 1888.) Yyy 27 



