52 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



from to the medial trochlea and thence stretching onto the forearm. 

 (See p. 79.) The part over the deltoid was again divisible at inser- 

 tion, one fascial sheet extending deep to the other. It should be 

 emphasized that in this genus the border of the panniculus carnosus 

 is practically fused with the border of the pectoralis, forming a 

 powerful sheet of muscle inclosing the trunk, which is of the greatest 

 importance in the economy of the animal. This is very different from 

 the condition in Phoca. In this Phoca the pectoral sheet was also 

 partially separable into three divisions but in a different manner, 

 and only toward insertion. Origin was from the midvental line 

 from the tough tissue dorsad of the entire presternal cartilage and 

 then ventrad of the whole bony part of the sternal complex. Thence 

 caudad origin passed laterad of the midventral line gradually to the 

 side near the hind limb. From these points the fibers converged to 

 the axillary region. Here it was found that the sheet from the pre- 

 sternum and sternum had become the most superficial, with insertion 

 upon the medial lip of the deltoid ridge, thence by fascia into the 

 axilla, and in the opposite direction, as far as the forearm. There 

 was a second, lateral part, narrow and with the fibers coming from 

 the region of the flanks, and in between these two a third division, 

 the fibers passing deep to the other two and inserting with the second 

 division and with the thicker, ventral part of the latissimus dorsi by 

 a single tough aponeurosis upon the medial lip of the deltoid ridge, 

 just deep to the first division. The sternal part of the pectoral 

 complex was robust, while the abdominal part was thinner. 



For Euiiietofias Murie reported a single superficial pectoral 

 (manubrium to fifth rib) inserting upon the proximal half of the 

 humerus and to the axilla, and a second layer (first rib to xiphoid) 

 with fascial insertion over the arm. In Odohenus he found a super- 

 ficial division from the presternal tip to the xiphoid and ending in 

 the fascia of the forearm, and a deeper, from the fourth costal 

 cartilage to 6 inches caudad of the xiphoid, with insertion upon the 

 whole length of the humeral shaft. In both of Murie's animals 

 there was a narrow third division, not differentiated by me in 

 Zdlo'phus, from the manubrium, which merged with the first division. 

 The differences in the pectorals reported by Miller are of a relatively 

 minor nature. Suffice it to say that in this order the pectorals are 

 exceedingly powerful and of great extent. 



There is some question regarding the proper treatment in many 

 mammals of the sheet of muscle of which the serratus magnus is a 

 part. In the human the serratus is usually considered as compris- 

 ing the entire muscle, but reference to the lower Mammalia indicates 

 that it would be wiser to treat it as two muscles. This has at times 

 been done, as by Reighard and Jennings ( 1901 ) , who term the ante- 

 rior division the levator scapulae, and I have therefore followed the 



