AKT. 15 ANATOMY OF THE EAEED AND EARLESS SEALS HOWELL 57 



M. obliqnus abdominis externus (figs. 16, 19) in the Zalophus origi- 

 nated from the last 10 ribs. From the sixth, seventh, and eighth 

 fhe respective digitations were well marked, but caudad therefrom 

 the slips were distinguishable only with diiRculty, they being very 

 tenuous and the fibers precisely parallel with those of the external 

 intercostals. The digitations were not in direct conjunction with 

 those of the serratus, but arose farther dorsad and deep to the latter. 

 Origin was also from the deep dorsal fascia for a short distance. 

 There was no Poupart's ligament, as there was in Eumetopias and 

 hence no direct connection with the iliac crest, but a sheet of tough 

 fascia running caudo-ventrad formed a part of the border of the 

 inguinal canal and inserted upon the tuber of the pubis. Insertion 

 was ectad of the rectus almost to the midventral line. 



In the Phoca this sheet arose from the last 13 ribs, the first few 

 digitations being rather involved in the relationship of their fibers. 

 They were in contact with part of the scalenus, depressor scapulae, 

 and serratus magnus. Caudad of the ribs the fibers of the dorsal 

 border were parallel and in contact with the ilicostalis lumborum or 

 lateral mass of the long system and connected to it by tough fascia. 

 The innominate border developed a Poupart's ligament. Insertion 

 was upon the midventral line ectad of the rectus. In Arctocephalus 

 this muscle seems quite similar to Zalophus save that insertion is 

 upon the brim of the pelvis, while that of Phoca vitulina is essentially 

 similar to my Phoca. 



M. obliqaus abdominis internas in the Zalophus arose from the cartila- 

 genous border of the thorax, from the deep dorsal fascia, from the 

 crural arch, extending from caudad of the ventral crest of the ilium 

 to the pectineal process, and then from the border of the pubis to 

 within several centimeters of the symphysis. Insertion was upon the 

 sheath of the rectus. That of the Phoca had a similar origin save 

 that the attachment was to Poupart's ligament rather than the brim 

 of the pubis direct. The fibers descended practically no farther 

 ventrad than the border of the rectus, and inserted upon the aponeu- 

 rotic sheet common to this and the transversalis. In Eumetopias the 

 only innominate connection mentioned was with the crest of the 

 ilium. 



M. transversalis abdominis in the Zalophus arose by interdigitations 

 with the fibers of the diaphragm, ostensibly as usual from the carti- 

 lagenous border of the thorax, the deep dorsal fascia, and with the 

 internal oblique from the crural arch. Insertion was upon the deep 

 part of the rectus sheath. In the Phoca this muscle did not extend 

 quite to the innominate but the fibers stretched almost to the mid- 

 ventral line. 



