96 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



tendons of the two long flexors which ran to the four lateral digits 

 entered from the deep side into four sheaths which stretched from a 

 part of the plantar fascia, as mentioned elsewhere. In the Phoca 

 this was an exceedingly robust muscle. It arose from the caudal 

 head of the fibula and from two-thirds of this aspect of the shaft, as 

 well as to a slight extent from the fibular part of the interosseous 

 membrane. .Muscle fibers ceased some 30 mm. proximad of the heel 

 and the verj^ broad tendon — the heaviest of the foot — passed over the 

 groove upon the greatly specialized posterior process of the a.straga- 

 lus, in this animal actually longer than that of the calcaneum. The 

 tone of this muscle and the form of astragalus — giving the action of 

 a regular tendo calcaneus — is all that prevents the foot from assum- 

 ing a platigrade position. The tendon of the flexor hallucis, after 

 appearing upon the plantar surface, broadened and passed between 

 the tendons of the plantaris and flexor digitorum longus, and partly 

 fused with the latter tendon ectad. It split apparently into four 

 branches, these going to digits 1, 3, 4, and 5. The one to the hallux 

 again split, one branch extending to the dorsum and the other to the 

 lateral side of this digit. This muscle is the flexor longus digitorum 

 of Murie, although Miller evidently failed to notice the fact. The 

 latter's descriptions are very inA'olved, and as he failed to dissect 

 apart the two layers of tendons, no differences of significance can be 

 noted. 



M. tibialis posticus (figs. 13, 27, 28) in the Zalophiis had fleshy origin 

 from the extreme medial part of the head of the fibula, from the 

 fibulo-tibial ligament mentioned under the flexor digitorum longus, 

 and from the entire posterior tibial fossa as far as the distal quarter 

 of the shaft. Its ver}^ large tendon passed over the most medial of 

 the two grooves upon the posterior aspect of the tibia, down the 

 medial border of the tarsus and metatarsus, and inserted broadly 

 upon the terminal phalanx of digit 1, this acting as an abductor of 

 the digit. Embedded in the tendon just mediad of the proximal 

 part of tarsale 1 was the tarsal sesamoid bone. In the Phoca the 

 flexor digitorum longus covered all but the medio-distal border of 

 this muscle. It was broad but tliin and arose chiefly from the poste- 

 rior tibial fossa for almost three-fifths of the length of the bone, 

 from the interosseous membrane mediad to the flexor hallucis longus, 

 and from the medial head of the fibula. Its rather small tendon 

 passed over the groove caudad to the medial malleolus and inserted 

 upon the lateral centrale. Miller evidently followed the tendon with 

 greater perseverance than I employed and ascribed to it considerable 

 complexity in its attachments over a limited area. 



M. tibialis anticus (figs. 13, 25, 26) Avas the most medial of the muscles 

 of the front of the shank. In Zalophus it was rather small and 

 arose from the head of the tibia, from the proximal half of its shaft. 



