74 PROCEEDINGS OF THE NATIONAL MUSEUM voc. 7S 



parently inseparable from the adjoining part of the lateral triceps. 

 It disappeared in fascia over the ulnar border of the forearm. The 

 more cranial division did not really constitute a distinct muscle but 

 was easily separable. It arose from the distal half of the central 

 ridge of the infraspinous space and was strongly inserted upon the 

 medial olecranon and (by fascia) onto the medial epicondyle of the 

 femur. In the Phoca I consider this muscle to have been single. 

 It arose from the dorsal third of the ridge upon the infraspinous 

 space and thence the line of origin curved about the adjoining part of 

 the vertebral border of the scapula as far as the spine, in contrast to 

 this part of the origin in the ZaXophus which was directed away 

 from the sj)ine. It^became very thick and passed over the elbow to 

 a rather abrupt insertion upon the superficial fascia of the forearm. 



M. triceps lateralis (figs. 7, 9, 10, 17, 20, 21, 23) in the Zalophus arose 

 partly from the aponeurosis covering the cranial portion of the 

 long head, but chiefly hj narrow fasciculi from the latero-caudal 

 neck of the humerus. The borders of this muscle were distinct but 

 the deep fibers blended with those of the medial head. With the 

 latter there was also some fibrous attachment to the olecranon but the 

 muscle finally passed over this and together with the adjoining part 

 of the long head was directed down the ulnar border of the forearm 

 and disappeared in fascia above the wrist (in fig. 20 the edge of this 

 part of the muscle is shown trimmed away). In the Phoca I list 

 this muscle as occurring in two divisions. The more lateral and the 

 one shown in figure 21 arose from an area that really constitutes the 

 latero-caudo-proximal border of the deltoid ridge, quite to the head of 

 the humerus. There is considerable question in my mind as to 

 whether the second division does not really belong with the triceps 

 longus — a point difficult to prove by the innervation. But the origin 

 was separated from that of the true long triceps by a considerable 

 interval and it seems more natural to place it with the lateral division. 

 It arose from the distal (cranial) third of the central ridge of tiic 

 infraspinous space, passed down the back of the brachium and joined 

 the first division, both inserting upon the more dorsal process of the 

 olecranon. 



M. triceps medialis (figs. 9, 10, 23) arose from the entire caudal part 

 of the shaft of the humerus and was continuous with the anconeus 

 externus. Insertion in both genera was upon the expanded radial 

 aspect of the olecranon, and slightly from the caudal or dorsal aspect 

 as well. 



Miller reported that in his Phoca and Arctocephalus conditions 

 were on the whole very similar to what I found in my seal and sea 

 lion, respectively, save that he divided the triceps into four parts — a 

 dorsi-epitrochlear corresponding to my first division of the long head 

 in Zalophus and long head in Phoca. In his Phoca origin was from 



