xvi PRIMAR Y FA CTORS OF ORGANIC E VOL UT1ON. 



PAGE 



Fig. 97. Psittacotherium multifragum Cope, mandibular ra- 



mus 329 



98. Diagrammatic representations of horizontal sections 



of tricuspidate molars of both jaws in mutual rela- 

 tion 333 



99. Deltatheriumfundaminis Cope, fragmentary skull . 336 



100. Centetes ecaudatus, skull and molars 337 



101. Inferior molar crowns representing transition from 



the simple to the quadritubercular 338 



102. Stypholophus whitice Cope ; apposition of inferior 



and superior molars 339 



103. Cynodictis geismarianus Cope ; skull 341 



104. Aelurodon sizvus Leidy; coadaptation of crowns of 



superior and inferior molars in mastication . . . 342 



105. Smilodon neogczus Lund ; skull 344 



106. Sections of crowns of molars of Ungulata .... 345 



107. Castorotdes ohioensis Foster ; skull 347 



108. Castoro'ides ohioensis Foster ; skull from below . . 350 



109. Ischyromys typus Leidy ; cranium and mandible . . 351 



i jo. Balcena mysticetus ; fore limb 353 



in. Feet of Amblypoda 354 



112. Feet of Proterotheriidae 358 



113. Dorsal vertebrae of merospondylous fishes .... 370 



114. Vertebral column of Eryops megacephalus Cope . . 371 

 1 140 Sleeve of coat 371 



115. Metatoceras cavatiformis Hyatt 406 



116. Do 407 



117. Temnochilus crassus 407 



118. Metacoceras dubium Hyatt 408 



119. Hyatt on Cephalopoda 410 



120. Diagram explanatory of Diplogenesis 441 



