Contents — Continued 



Page 



Ontogeny of Primary and Secondary Dentitions 73 



Primary Teeth 74 



Secondary Teeth 80 



Ontogeny and Phylogeny of Canine Migration 83 



Comparative Dental Formulae 83 



Gingival Eruption of Secondary Teeth 85 



General Structure of Secondary Teeth 86 



Dentin 87 



Dental pulp 90 



Cementum 90 



Shape, Orientation, and Occlusion of Cheek Teeth 92 



Growth, Attrition, and Abrasion of Cheek Teeth 96 



Linear growth 96 



Attrition and abrasion 96 



Form, Development, and Abrasion of Tusks 104 



Basic form and structure 104 



Relation of hypercementosis to tusk development 108 



Orientation and shape of tusks Ill 



Linear growth, abrasion, and fracture of tusks 114 



Abraded surfaces of tusks 127 



Missing and anomalous tusks 132 



Function of Tusks 134 



Relation to feeding 134 



Relation to social behavior 135 



Other functions 136 



Food and Feeding Behavior 138 



Diet of Calves and Other Young Animals 138 



Length of the suckling period 138 



Composition of walrus milk 141 



Rate of intake of milk 142 



Diet After Weaning. 145 



Kinds of prey 145 



Seasonal and regional diets 154 



Rate of intake of food per day r. . . 157 



Feeding Behavior 161 



Feeding rhythm 161 



Depth and duration of feeding dives 161 



Search for food 163 



Selection of prey 165 



Ingestion of prey 165 



Reproduction 172 



Definitions 173 



Reproductive Organs 174 



Male 174 



Female 175 



ill 



