286 ZALOPHUS CALIFORNIANUS CALIFORNIAN SEA LION. 



Dentition. The teetli in Zalophus are all strongly devel- 

 oped and very firmly implanted. All are single-rooted except 

 the last molar, which is imperfectly double- rooted. The molars 

 all have a distincly beaded cingulum on the inner side. The 

 lower molars and the fifth and sometimes the fourth up]3er 

 molars have a small but distinct anterior cusp. The canines 

 and the incisors present the usual form seen among the Otaries. 



The teeth of a middle-aged male skull present the following 

 measurements : 



Measurements of the Teeth. 

 A. Teeth of the Upper Jaw. 



B. Teeth of the Lower Jaw. 



The molars are usually closely approximated, but sometimes 

 there is a small space between the two hindermost of the series, 

 and occasionally they are all slightly and evenly spaced. The 

 hinder edge of the last upper molar is generally anterior to or 

 about even with the posterior border of the zygomatic process 

 of the maxillary. When more than five upper molars are pres- 

 ent, the sixth or supernumerary is posterior to the fifth, and is 

 usually smaller than the fifth (sometimes almost rudimentary) 

 and lacks the accessory cusps seen in the fifth. 



The milk dentition (fully represented in three skulls before 

 me and partly so in five others) does not differ from that of the 

 other species of the family, and has been already fully described 

 (see antea^ p. 223). 



