ABT. 15 ANATOMY OF THE EAEED AND EAKLESS SEALS HOWELL 81 



M. extensor metacarpi poUicis (figs. 10, 20, 21) arose in the Zalophus 

 from the whole of the fossa of the lateral ulna that was situated 

 upon the radial side of its prominent lateral ridge, and extemled in 

 origin two thirds the length of the shaft. It ran obliquely across 

 the radius and its tendon passed through the large groove upon the 

 cranio-lateral termination of the radius. It then passed to a double 

 insertion, the first to the medial base of metacarpus 1, and the other 

 to the first phalanx of the same digit. In the Phoca- it arose from 

 the Avhole of the lateral face of the olecranol plate save the extreme 

 ulnar tip. Its tendon inserted as normal upon the base of metacar- 

 pus 1. This was termed extensor ossi metacarpi poUicis by Murie 

 and Miller. From the former's description, insertion in Eumetoplas 

 and Odohenus seems to have resembled that in my Phooa, but the 

 tendon was much weaker in the latter animal. 



M. extensor poUicis longus (figs. 10, 20, 21) in the ZaIop?ius arose 

 from that part of the fossa on the lateral ulna that was situated upon 

 the ulnar side of its prominent ridge. Its very broad tendon ex- 

 tended obliquely across the carpus and was inserted upon the dor- 

 sum of the first phalanx of the poUex. In the Phoca it arose from 

 the ulnar tip of the lateral olecranon and for some little distance 

 distad, while insertion was as in Zalophus. For Eumetopkis Murie 

 termed this muscle extensor pollicis et indicis but noted no differ- 

 ences, and it is Miller's extensor j)rimi internodii pollicis. In the 

 latter's Phoca vitulina origin was from the posterior third of the 

 ulna. 



M. extensor carpi ulnaris (figs. 9, 10, 20, 21) in the Zalophus appeared 

 'very similar in its proximal portion to the extensor communis. It 

 arose by aponeurosis from the radial two-thirds of the olecranol 

 border of the ulna beneath the lateral anconeus. Its rather slender 

 tendon passed to the lateral manus and was inserted upon the lateral 

 border of metatarsus 5. In the Phoca origin was from the lateral 

 epicondyle of the humerus, while insertion was normal as in 

 Zalophus. 



M. extensor carpi radialis (figs. 9, 10, 20, 21) was single in its muscular 

 portion and arose from just dorsad of the lateral epicondyle proper. 

 It extended next laterad to the supinator longus and its tendon was 

 seen to be double. In the Zalophus these are doubly inserted into 

 the lateral border of metacarpus 1 and the medial border of metacar- 

 pus 2. In the Phoca one tendon went to metacarpus 2 and the other 

 sent two branches to metacarpals 2 and 3 respectively. As this inser- 

 tion was different from anything reported for the genus, I was 

 careful to verify it. Miller wrote that in Phoca vitulina insertion 

 was upon the first and second metacarpals, while in P. harhafa- it was 

 upon the second only. 

 86377—28 6 



