42 



PROCEEDINGS OF THE JSTATIONAL MUSEUM 



TOL. 73 



of the Phoca lacks any such constriction. As might be expected 

 from the great caudad development of the astragalus in the phocid 

 the caudal process of the calcaneum is correspondingly reduced in 

 robustness, which is not the case in the otariid. In the latter the 

 anterior and posterior facets (the anterior and middle facets of man 

 are fused in the Pinnipedia) are less extensive than in man, and still 

 smaller in the phocid. Dorsad in the Phoca only there are two deep 

 grooves, the more medial for the tendons of the peronei brevis and 

 digiti quinti, and the more lateral for the peroneus longus. In the 

 otariid only the expanded distal portion allows slight contact with 

 the centrale. 



The centrale of Zalophus is flat in a cranio-caudal direction but 

 broad transversely, while in Phoca it is more irregular, is relatively 

 narrow transversely and deep dorso-ventrad, making the narrowest 



— CALCANEU/A 

 ASTRAGALUS— 

 CEMTRALE-^ 



-CUBOID 



SESW^OIO. 



TARS ALES — 

 nETATABSI 



-doesal view of left tarsus and metatarsus of 

 Zalophus (Z) and Phoca hispida (P) 



part of the tarsus through the centrale-cuboid, while in the otariid 

 it is across the neck of the astragalus and through the calcaneum. 



The lateral part of the cuboid is deeply grooved in Phoca only, 

 for the passage of the peroneus longus tendon, and the whole bone 

 is not only more irregular in shape, but relatively a bit larger than 

 in the Zaloyhus. 



Tarsale 1 is very large, corresponding to the size of the hallux, 

 but lies considerably more laterad (less dorsad) in the Phoca. In 

 both animals tarsale 2 is slightly smaller than tarsale 3. Mediad to 

 and fairly between tarsale 1 and the centrale of Zalophus is a well- 

 defined sesamoid bone. It is mostly embedded in the tendon of the 

 tibialis posticus but in adults its position is osteologically indicated 

 by small but distinct articular facets upon both bones. In the Phoca 

 dissected there was apparently no sesamoid occurring as a real bone, 



