REPORT ON THE SEALS. 



199 



The Solcus is found in Arctoccphalus gazclla, but not in the Phocinae and Macrorhinus. It is a 

 flattened elongated muscle, lying on the peronei brevis and quinti digit! Near the head of the 

 fibula it is a fine sheet, at the middle triangular, the apex being the origin, the base the free edge ; 

 over the posterior fifth it is a fleshy bundle. It arises from the dorsal surface of the head of the 

 fibula by a thin tendon, from the whole length of the inner border of the shaft by a fine aponeurosis, 

 and by muscular fibres from the inner surface of its posterior fifth, ve.itral to this border and dorsal 

 to the interosseous membrane. The fibres pass backwards, and are inserted into the proximal 

 surface of the tuberosity of the os calcis beneath the attachment of the gastrocnemius extending 

 further back on the dorsal side of the bone, and on nearing the lower or posterior border of the 

 fibula the inner surface becomes tendinous. It has the same action as the gastrocnemius. Murie 

 gives an origin from the outer condyle of the femur which I did not observe. 



The Plantaris in the Phocinae lies below the gastrocnemius. It arises, as already mentioned, from 

 the femur with the outer head of the gastrocnemius, and descends along the ventral side of the 

 flexor longus hallucis, at the lower third of the leg it crosses to the dorsal side of the above muscle, 

 and enters the plantar surface between the gastrocnemius and the flexor longus hallucis, below the 

 backward prolongation of the tendons of the gracilis, semimembranosus, and semitendinosus which 

 form the plantar fascia. Beneath this it widens, and is moored to the dorsal side of the larger 

 combined tendon of the flexor longus hallucis and the flexor longus digitorum. Before reaching 

 this tendon, the accessorius is inserted into its dorsal side (fig. II., p. 201). It sends one slip, behind 

 its union with the combined tendon, to the distal end of the inner surface of the 5th metatarsal bone. 



In Macrorhinus leoninus it arises alone from the same 

 part of the femur as the outer head of the gastrocnemius 

 and the plantaris in PJwca vitulina. It blends with the 

 insertion of the gluteus maximus on its outer side at the 

 origin. At the os calcis it enters the pes, as in Phoca vitu- 

 lina, and joins the dorsal side of the conjoined plantar 

 tendon of the flexor longus digitormn and the flexor longus 

 hallucis (fig. IV., p. 202). 



In Arctocephalus gazella it is one-third the size of the 

 gastrocnemius, and arises, in common with the popliteus, 

 from the external border of the femur to the point of its 

 tendon from the external condyle. It courses backwards, 

 lying upon the soleus, partially covering the gastrocnemius, 

 and is situated on the dorsal side of the leg. Near the ankle 

 it forms a round tendon, wlndi occupies the groove on the os 

 calcis to the ventral side of the gastrocnemius. One inch 

 posterior to the distal end of the os calcis it widens and 

 divides into an anterior and posterior slip. The anterior 

 joins the plantar fascia (fig. I.). The posterior divides into 

 four slips, which are the superficial perforated tendons for 

 the 2nd, 3rd, and 4th digits. In the Phocinae it is supplied by the great sciatic nerve. 



The Deep Group in all the specimens is alike. The muscles are the popliteus, flexor longus 

 hallucis, flexor longus digitormn, with its accessorius and lumbricales, and the tibialis posticus. 



T.P. 



jinnnJ 



PLF. 



Fig. I. — The plantar fascia of Arctocephalus. 

 Sm, semimembranosus ; St, semitendinosus ; 

 PI. , plantaris ; T.P., tibialis posticus ; 

 Pl.F., plantar fascia. 



