REPORT ON THE SEALS. 



201 



inner surface of the posterior extremity of the tibia, dorsal to the tibial groove, and at the posterior 

 border of the os caleis blends with the flexor longus digitorum. The insertion comes after the 

 insertion of the flexor longus digitorum in the Phocince and Macrorhinns. 



In Arctoccphalus the inner surface of the tibia differs from other Seals ; for upon the posterior 

 third of the shaft is a border intermediate between the ventral and dorsal borders, and it is to 

 it that the origin of the flexor longus hallucis changes from the dorsal border. In Otaria and 

 TrMicchus it arises from the fibula only. In the Phocinse it is supplied by the great sciatic nerve. 



The Flexor longus digitorum is the flexor quatuor digitorum of Lucae. In the Phocinre it is a 

 triangular muscle, and arises from the triangular surface of the fibula to the dorsal side of the 

 interosseous membrane behind the tibio-fibular fusion, and from the popliteal line on the inner 



JZH PI 



FLB 



FLD. 



SP 



SP 



J7ZB 



ELD 



Fig. III. — Tendons of the foot of Arctocephahis. 

 FLD, Flexor longus digitorum ; FLH, Flexor 

 longus hallucis. 



SP n 



Fig. II.— Tendons of the foot in the Phocina;. FLD, Tendon of 

 Flexor longus digitorum ; FLU, Tendon of Flexor longus 

 hallucis ; PI, Tendon of the Plantaris ; Ac, Insertion of the 

 Accessorius ; Gr, Tendinous slip from the plantar fascia, which 

 is formed by the Gracilis, Semimembranosus, and Semiten- 

 dinosus ; S, Tendinous slips to the flexor tendon sheaths ; SP, 

 Flexor sublimis digitorum (perforates) ; D, Flexor profundus 

 digitorum (perforans) ; M, Teudinous slips to the metatarsal 

 bones. 



surface of the tibia behind the insertion of the popliteus to the middle of the shaft. The tibialis 

 posticus lies to its dorsal side, and the ventral border of the flexor longus hallucis behind. It forms 

 a tendon which crosses to the dorsal border of the tibialis posticus, and enters the dorsal furrow in 

 the large groove above the internal malleolus beneath its division of the annular ligament. 



In Macrorhinns leoninus it is different, for there is a large popliteal line, and it arises from the 

 whole of it. The ventral tuberosity of the tibia forms more of the. internal surface than in the 



(zool. chall. zxp. — paet lxviii. — 1888.) Yyy 26 



