ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



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Fig. 88. Diagrammatic views of the patterns of abrasion and decrement of the clin- 

 ical crown of a tusk from a 15-year-old female Pacific walrus: (a) anterior, medial, 

 posterior, and lateral aspects of the right tusk, showing paths of abrasive particles 

 (arrows) and resultant exposure of the deep tissues; and (b) cross-sections of the same tusk 

 at 10-cm intervals. 



(Figs. 88fl; 90, center). On the posterior surface, the striae tend to converge 

 obliquely distad. 



The pattern of striae described above is evident on most tusks along the full 

 length of the clinical crown. It tends to be most clearly expressed on the tusks of 

 females and immature males; in adult males, it sometimes is obscured by massive 

 engraving by coarser particles with no predominant orientation of striae. Pitting 



