Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

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Text Appearing Before Image: is gradually changed,and its base becomes anchylosed to the shallow cavity of thealveolar surface of the bone. In the posterior part of the largemucous sheath of the poison-fang, the successors of this toothare always to be found in different stages of developement;the pulp is at first a simple papilla, and when it has sunk intothe gum the succeeding portion presents a depression along its TEETH OF REPTILES. 399 inferior surface, as it lies horizontally, with the apex directedbackward ; the capsule adheres to this inflected surface of thepulp; and the base of the groove of the loose growing poison-fan £ is brought into the same relation with the duct of thepoison gland as the displaced fang, which has been severed fromthe duct. The existing species of Lizards differ from those of Crocodilesin the anchylosed condition of the teeth, which present few modi-fications of importance : those that yield most fruit to physiology,and which have most expanded our ideas of the extent of the 271

Text Appearing After Image: Skull of Dicynodon lacerticeps, one third natural size resources of Nature and the exceptional deviations from whatwas deemed the rule of structure in the Saurian dentition,have been discovered by the study of the fossil teeth of extinctforms of the order. Amongst these the most extraordinary arethose called 6 Dicynodonts,1 from their dentition being reducedto one long and large canine tooth on each side of the upperjaw. These teeth recall, at first sight, the character which thelong poison-fangs give, when erected, to the upper jaw ofthe Rattle snake. The alveolar border of the lower jaw and ofthe premaxillary part of the upper jaw is trenchant, and seemsto have been sheathed with horn. The maxillary, fig. 271,21, is excavated by a wide and deep alveolus, with a circulararea, and lodges a long and strong, slightly curved, and sharp-pointed tusk, which projects about two thirds of its length from 1 Erom 5ts, two, and kvpSSovs, the name given by Hippocrates to the canine teeth,and sign

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