84 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 73 



A small slip also separated from this mass to insert upon the psoas 

 process of the ventral ilium. The homology of this large mass of 

 muscle is very uncertain, but it may provisionally be termed psoas 

 tertius. (Figs. 11, 24.) 



Murie considered that in Eumetopias either the two psoas muscles 

 had fused or the true psoas minor was absent, the two muscles of 

 this group therefore consisting of a psoas and an iliacus. For Odo- 

 henus he said that the two psoas were closely united, and inserted by 

 a common tendon upon the ilio-pectineal eminence — an interpreta- 

 tion that is open to question. 



M. iliacus (figs. 11, 12, 13, 24) was not entirely distinct. In the 

 Zaiophus it was very small, arising from the ventral border of the 

 ilium in intimate relation Avith the final slip of the quadratus luni- 

 borum. It inserted with the psoas magnus upon the lesser trochanter. 

 In the PJwca its fibers were inseparable from the part of the psoas 

 tertius which joined the ventral ilium, while insertion was with the 

 psoas magnus upon the medial tuberosity of the tibia. This muscle 

 seems invariably to be present in pinnipeds. 



M. tensor fasciae femoris (figs. 12, 17) arose from the lumbodorsal 

 fascia, in the Zaiophus reaching the middorsal line over the last 

 two lumbar vertebrae. In the Phoca the exact bounds of the muscle 

 could not be so well defined because of the condition of the specimen. 

 Insertion in both was upon the lateral part of the patella. 



M. gluteus maximus (figs. 12, 16, 17) in the Zal-ophus had origin con- 

 tinuous craniad with the biceps femoris over the spines of the three 

 sacral vertebrae. It passed over the proximal part of the greater 

 trochanter, to be inserted upon the disto-lateral part of the same^ 

 but not appreciably onto the shaft of the femur. In the Phoca this 

 muscle was very heavy, indeed, and arose by aponeurotic fascia 

 over the middorsal space included between all four sacral and first 

 tAvo caudal vertebrae. It quickly converged to a tendinous insertion 

 along the entire lateral border of the shaft of the femur from the 

 lateral condyle to the distal part of the gi-eater trochanter, although 

 over the middle of this space there seemed to be no actual attachment 

 to the bone. In both Ewinetopias and ArctocephcHus two heads were 

 reported, but the separation seems to have been incomplete. At anjr 

 rate, insertion was upon the shaft of the femur as well as the greater 

 trochanter, thus resembling the condition in my Phoca rather than 

 the Zaiophus. Miller wrote that in Phoca vitulina there were also- 

 two heads and that one of them arose from the ilium. 



M. gluteus medius (figs. 11, 12, 16, 17) in the Zaiophus arose from 

 the anterior border of the ilium, and this part was not covered by 

 the gluteus maximus. Near the insertion it was separable, except 

 at its ventral border, into two thin sheets, these forming a V-shaped 

 tendinous attachment to the greater trochanter. In the Phoca this 



