94 PROCEEDINGS OF THE NATIONAL MUSEUM vol.78 



longus tendons extending to the four lateral digits. These last 

 entered the sheaths from their deep sides near the metatarsal-phalan- 

 geal joints. In the Phoca the plantaris was much larger than the 

 lateral, but smaller than the medial, gastrocnemius. It had an ex- 

 tensive fleshy origin from the caudal surface of the lateral epicondyle, 

 the head being really separable into two parts, one arising from the 

 ridge at this point and the other from the slight furrow adjoining. 

 Its slender tendon passed mediad from beneath the gastrocnemius 

 and over the depression between the calcaneum and astragalus. It 

 then extended not to the superficial layer of the plantar fascia but 

 deeper, to an attachment upon the plantar surface of the flexor 

 hallucis longus. Its tendinous fibers continued, however, appar- 

 ently to the fourth digit only. 



M. soleus (figs. 13, 25, 27) is present in the otariids only. In 

 Zalophus it was very thin at origin and robust at insertion. It arose 

 by aponeurosis from the head of the fibula and by muscle fibers from 

 the caudal border of the shaft as well as from the aponeurosis cover- 

 ing the peroneus brevis. Insertion was entirely fleshy upon the dor- 

 sal surface of the calcaneal extension deep to the tendon of the 

 gastrocnemius. This muscle was very closely involved with the 

 peronei brevis and digiti quinti. It is lacking in the Phocidae. 



M. popliteus (figs. 12, 13, 27, 28) in the Zalophiis was extensive but 

 thin. Origin was by a tough tendon from the depression between 

 the lateral condyle proper and the condyloid ridge, and by muscle 

 fibers from the capsule of the joint, and was in intimate relationship 

 with the plantaris. The belly expanded as usual and near the in- 

 sertion, esi3ecially proximad, it divided into two thin sheets to allow 

 for the passage of the internal lateral ligament. Insertion was upon 

 the medial border of the shaft of the tibia from a point slightly 

 distad of the head practically to the center of the shaft, but there 

 was no osseous indication of its position. In the Phoca tliis muscle 

 was rather thick but relatively narrow. Its tendon arose from the 

 pit cradiad of the lateral condyle, origin being a bit smaller than in 

 Zalophus, and some of the muscle fibers also arose from the capsule 

 of the joint. Insertion was less than 25 mm. in length and at quite 

 some distance from the head. 



The flexor and extensor tendons to the digits have a habit, in 

 diverse sorts of mammals, of wandering about, and the homolog-ue 

 of a hallucis or a digiti quinti muscle may be found to extend to- 

 some other digit besides the hallux or the fifth digit, respectively.. 

 Hence one can not always judge by insertion, nor by origin either,, 

 regarding the name of a muscle. When the innervation is not diag- 

 nostic the matter may become extremely difficult. Such is the state 

 of affairs concerning the long flexors of Zalophus and Phoca. The 

 one that extends to the hallux in the former does not do so in the 



