1898.] NATURAL SCIENCES OF PHILADELPHIA. 199 



is 278 mm. In a very old male specimen of obesus from Alaska 

 these measurements are respectively 220 mm. and 295 mm. In a 

 somewhat younger but adult west Greenland specimen of rosmarus 

 these dimensions are 195 mm. and 295 mm. Viewed anteriorly, 

 the facial outline of the fossil specimens, especially in the oldest 

 New Jersey example, shows affinity with the rosmarus type in the 

 relatively greater ratio of width to height, and in the Sable Island 

 skull the median projection of the premaxillaries extends consider- 

 ably beyond the anterior plane of the maxillaries into a blunt, beak- 

 like process. 



In the very old recent Alaskan specimen the premaxillaries are 

 on a plane with the maxillaries at this point, and their median su- 

 ture recedes behind them at its anteroinferior border in a sort of 

 hare-lip conformation. 



The three fossil specimens are remarkable for the great relative 

 size of the nasal bones. The New Jersey specimen now belonging 

 to the Geological Survey of that State is much wider across the 

 maxillaries than the widest recent or fossil walrus skull in the cus- 

 tody of the Academy, and is from a very old individual. While 

 we would expect a corresponding width of the nasal bones, these 

 are, nevertheless, correspondingly long, also, presenting an area 

 nearly twice as great as in the largest recent walrus skulls in the 

 collection. The smaller New Jersey specimen, belonging to the 

 Academy, also has a correspondingly large nasal area. The nasal 

 sutures in the process of fossilization become sufficiently well-defined, 

 even in the oldest specimens, to determine their area. In the larger 

 New Jersey specimen the greatest nasal length is 98 mm., and the 

 greatest width 80 mm. In the smaller one these dimensions are 96 

 mm. and 81 mm. In the largest Greenland specimen they are 72 

 mm. and 65 mm., and in the largest Alaskan specimen 72 mm. and 

 64 mm. 



Turning now to the upper maxillary dentition, a comparison be- 

 tween the fossil and recent specimens of aged individuals shows the 

 following marked differences in the permanent teeth. 6 



In recent rosmarus of nearly the same size as the smaller New 

 Jersey fossil specimen and 25 mm. shorter in basilar length than the 

 Nova Scotia fossil, all the grinding teeth average about one-half 

 the dimensions of the fossil specimens, and making allowance for 



6 I adopt the dental formula of Dr. Allen's Monograph of the Pinnipeds, 

 page 57. 



