362 THE ANATOMY OF VERTEBRATED ANIMALS. 



zontal, and the synchondrosis between the basisphenoid and 

 presphenoid persists. In all these respects the Seal's skull is 

 strikingly cetacean. In fact, if the supra-orbital processes 

 were sawn off, a Porpoise's brain-case would closely resemble 

 a Seal's. But the nasal bones and the parietals are large, and 

 the ethmoidal region is very peculiar. The lamina ■perpen- 

 dicularis is largely ossified, and the vomer soon becomes ossi- 

 fied into one mass with it. The two ethmoidal turbinals (or 

 the superior and middle) are small and flattened, and the lat- 

 ter anchyloses with the vomer on each side. The inferior, or 

 maxillary, turbinal is extremely large and complicated, and it 

 blocks the nasal passage in front of the others like a sieve, or 

 strainer. There is no lachrymal bone, but the jugal is large. 

 The squamosal is anchylosed with the periotic and tympanic. 

 The latter is massive and shell-shaped, somewhat as in the 

 Cetacea^ but it has rather different relations to the auditory 

 meatus. The periotic is very large, and its tumid pars mas- 

 toidea appears largely on the exterior of the skull. The fossa 

 under the superior vertical semicircular canal is prolonged into 

 this tumid part of the periotic. 



The alveolar portions of the premaxillse are very small, but 

 these bones extend far up the sides of the anterior nares. 

 The maxillas do not extend over the frontals. The mandible 

 has a well-developed coronoid process. 



The pollex is the longest and strongest digit, the others 

 gradually decreasing in length. The fifth metacarpal articu- 

 lates with the cuneiform bone, as well as with the unciform. 



The ilium is short, and the long pubis and ischium are 

 greatly inclined backward, so that the long diameter of the os 

 innomi7iatwn makes only an acute angle with the spine. The 

 femur is much shorter than the humerus. The tibia and fibula 

 are anchylosed, and more than twice as long as the femur. 

 The pes is longer than the tibia. The astragalus has a pecul- 

 iar, roof-shaped, tibial surface, and sends a process backward 

 which contributes to the formation of the very short heel. 

 The hallux is the strongest of the digits ; while this and the 

 fifth digit are the longest of those of the pes. 



The cutaneous muscle is largely developed and inserted 

 into the humerus. The pectoralis major is very large, and 

 arises from each side of the prolonged manubrium, and even 

 in front of it, beneath the neck ; the fibres of the muscles of 

 opposite sides are continuous. The pahnaris longus is a strong 

 muscle, but the proper digital muscles are weak or absent, as 

 in the case of the abductor^ adductor^ flexor brevis, and oppO' 



