208 THE VOYAGE OF H.M.S. CHALLENGER. 



metatarsal bones, crosses the 4th metatarsal, and is inserted by a fine tendon into the tibial side of 

 the base of the 1st phalanx of the 5th metatarsal. 



In Arctocephalus the Adductor hallucis and the Adductor minimi digiti arise by a common origin 

 from the plantar surfaces of the proximal ends of the 2nd, 3rd, and 4th metatarsal bones, and from 

 the sheath of the peroneus longus by a tendinous sheet which is semi-circidar. Along the posterior 

 border of this tendon muscular fibres spring and take the form of a horse-shoe, the two limbs 

 forming these two muscles. The tibial lirub is the adductor hallucis and is inserted into the fibular 

 distal end of the 1st metatarsal. The fibular limb is the adductor minimi digiti and is inserted 

 into the distal tibial side of the 5th metatarsal. 



In Otaria these muscles are regarded as superficial interossei, and their origins are more extensive 

 than in Arctocephalus. In Trichechus (Murie) they are similar to Otaria. In Trichecus Cunningham 

 says they form the plantar layer, and he figures the adductor hallucis as consisting of two parts — 

 an adductor obliquus and an adductor transversus, but I did not find the transverse head of the 

 adductor hallucis, and the adductor rninimi digiti was not a separate fasciculus, as he figures it. The 

 general plan of origin in the two specimens of Arctocephcdi was like Murie 's drawings, the adductors 

 being combined at their origins. 



The Adductor ossis metatarsi primi in Arctocephalus arises from the anterior third of the tibial 

 side of the plantar surface of the 2nd metatarsal, crosses to the 1st digit, and is inserted into the 

 1st phalanx on its fibular proximal side. 



The Flexorcs breves. — These are named the deep interossei by Dr. Murie, and form the inter- 

 mediate layer of Professor Cunningham. In Phoca vitidina and in Arctocephalus the muscles of 

 the 2nd, 3rd, and 4th digits are double, of the 5th single, and the 1st digit is peculiar. 



In Phoca vitidina they are feeble and arise from both sides of the plantar surfaces of the 2nd, 3rd, 

 and 4th metatarsals, and from the tibial side only of the 5th. The muscle from the tibial side of the 

 2nd digit also has origin from the fibular proximal end of the 1st metatarsal. They are inserted 

 into the proximal ends of the first phalanges of the digits, on the same sides from which they spring. 



In Arctocephalus they are well developed. The origins and insertion are as in Phoca vitulina, 

 with one exception — the muscle from the tibial plantar surface of the 2nd metatarsal is only from 

 the posterior two-thirds of the shaft. 



The Flexor brevis primi metatarsi or flexor brevis hallucis. In Phoca vitulina the outer muscle 

 or outer head arises from the fibular side of the 1st metatarsal, and is inserted into the proximal 

 fibular side of the 1st phalanx of the 1st digit. The inner flexor or inner head in Otaria is named 

 the adductor hallucis, in Trichechus (Murie) the flexor brevis hallucis, and in Trichechus 

 (Cunningham) this slip was not found. In Phoca it arises beneath the adductor hallucis from the 

 outer posterior third of the scaphoid bone, upon the tendon of insertion of the tibialis posticus, and 

 from the anterior outer third of the entocuneiform. It is a glistening tendinous band, with a 

 reddish tinge at the anterior end, which passes backwards and inwards and is inserted into the 

 inner side of the base of the 1st metatarsal. 



In Macrorhinus the inner head arises from the outer posterior half of the scaphoid bone in 

 common with the outer head of the abductor hallucis, over the middle of the entocuneiform bone 

 the tendon splits into two equal portions — the inner is the abductor hallucis, the outer forms the 

 flexor brevis hallucis. It is inserted into the proximal tibial plantar surface of the 1st metatarsal 

 to the outer side of the abductor hallucis. 



