ART. 15 ANATOMY OF THE EAEED AXD EARLESS SEALS HOWELL 87 



MUSCLES OF THE THIGH 



There was evident a decided tendency toward fusion of the gracilis, 

 semimembranosus, and semitendinosus of Phoca^ and the three to- 

 gether formed a great muscle mass with a single prime function. 

 No such tendency was found in Zaloflius. 



M. sem'.membranosus (figs. 11, 13, 24) of Zcdophus occurred in two 

 parts. The posterior (really the inferior) arose from the caudal 

 border of the ischimn adjoining the symphysis and the origin of 

 the gracilis. Insertion was narrow and fascial beneath the caudal 

 border of the gracilis. The anterior division, of about the same size, 

 arose from the caudal border of the ischium dorsad of the origin of 

 the posterior part. Fascial insertion upon the cranial border of the 

 tibia was entad of the cranio-dorsal border of the gracilis and was 

 entirely hidden by the latter. In the Phoca this muscle was single 

 and arose along the caudal border of the ischium, the more caudal 

 part being incompletely separable from the gracilis, under cover of 

 which muscle it extended to a fleshy insertion not directly upon the 

 tibia but upon the heavy aj^oneurosis investing the ventral belly of 

 the semitendinosus. For both Eum^topias and Odol^enus Murie 

 called this muscle semitendinosus. In Arctocephalus it was single, 

 while Miller reported it double for Phoca. 



M. semitendinosus (figs. 11, 13, 16, 17, 24) in the Zalophus arose from 

 over the spines of the third to sixth or seA^enth caudal vertebrae, with 

 fascial insertion upon the distal quarter of the shaft of the tibia (not 

 including the malleolus). In the Phoca it occurred in two parts 

 which were entirely distinct at origin but apparently fused more 

 distad. The posterior division was the more superficial and much 

 the larger. It arose robustlj^ from the transverse processes of the 

 first three caudal vertebrae. The anterior division arose by tendi- 

 nous fascia from the caudal border of the ischium along an area 

 adjacent to the semimembranosus but not reaching the dorsal spine. 

 The insertional end of both parts together developed a stoufe aponeu- 

 rosis attached along the cranial border of the tibia and the ham- 

 string tendon. This is the muscle which Murie termed semimem- 

 branosus. It was single also in Odohenus^ Eumetopias^ and Arctoce- 

 phalus. 



In both animals the aponeurosis of insertion of these hamstring 

 muscles ended in the tough fascia and connective tissue over the heel. 

 In Phoca especially it may be said to end in a sort of ligament which 

 extended from the head of the fibula to the most prominent part of 

 the external malleolus, and there was also substantial anchorage in 

 the fibrous tissue beneath the calcaneal tendon. 



M. biceps femoris (figs. 11, 12, 13, 16, 17) in the Zalophus occurred in 

 three main parts. The more superficial portion of the long head was 



