Geological magazine . eeth are not displaced vertically by their successors, butfrom the side. The crown of the young tooth, also with two strongroots, cuts its way between the alveolar margin and the adjacentroot of the old tooth, sometimes advancing between the two roots,as might be expected. The teeth in this family are entirely confined to the maxillaryand dentary bones. The rostral bone, the premaxillaries, and thepre-dentary, are entirely edentulous. Cervical and Dorsal Vertebra.—The atlas and axis of Tricera-tops are coossified with each other, and at least one other vertebrais firmly u
Geological magazine . eeth are not displaced vertically by their successors, butfrom the side. The crown of the young tooth, also with two strongroots, cuts its way between the alveolar margin and the adjacentroot of the old tooth, sometimes advancing between the two roots,as might be expected. The teeth in this family are entirely confined to the maxillaryand dentary bones. The rostral bone, the premaxillaries, and thepre-dentary, are entirely edentulous. Cervical and Dorsal Vertebra.—The atlas and axis of Tricera-tops are coossified with each other, and at least one other vertebrais firmly united with them (Woodcut, Fig. 1). These form a solidmass, well adapted to support the enormous head. The cup for theoccipital condyle is nearly round, and very deep. The rib of thesecond vertebra is coossified with it, but the third is usually centrum of the fourth vertebra is free, and the remainingcervicals are of the same general form, all having their articularfaces nearly flat (Woodcut, Fig. 2). 2. Fig. 1.—Anterior cervical vertebrae of Triceratops porosus, Marsh ; side view. Fig. 2.—Fourth cervical vertebra of same series; back view. a. anterior face of atlas ; d. diapophysis ; n. neural canal; p. posterior faceof fourth vertebra; r. rib ; s. neural spine of axis ; s. neural spine of thirdvertebra ; s. neural spine of fourth vertebra ; z. posterior zygapophysis. The anterior dorsal vertebrse have very short centra, with flatarticular ends, and resemble somewhat those of Stegosaurus, especiallyin the neural arch (Woodcut, Figs. 3-4), 196 Trof. 0. C. Marsh—Gigantic Cerafopsidce. The posterior trunk vertebras have also short, flat centra, but thediapophyses have faces for both the head and tubercle of the ribs,as in Crocodiles, a feature not before seen in Dinosaurs (Woodcut,Figs. 5-6).
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1864
