. Carnegie Institution of Washington publication. IM-'SMATOCII ELYID I . t8< I'his genus is a most interesting one, inasmuch as it shows evident relationships with the Cheloniidae, and at the same time presents characters which must he regarded as more primitive than those of the latter family. Among these characters is the possession of well-developt nasal bones. The choanae too have their primitive position just behind the premaxillae and are separated by the body of the vomer. In the Cheloniidae the latter bone sends downward a perpendicular plate, the lower border of which expands later
. Carnegie Institution of Washington publication. IM-'SMATOCII ELYID I . t8< I'his genus is a most interesting one, inasmuch as it shows evident relationships with the Cheloniidae, and at the same time presents characters which must he regarded as more primitive than those of the latter family. Among these characters is the possession of well-developt nasal bones. The choanae too have their primitive position just behind the premaxillae and are separated by the body of the vomer. In the Cheloniidae the latter bone sends downward a perpendicular plate, the lower border of which expands laterally and joins horizontal plates of the maxillae and ot the palatines, forming a floor beneath the narial passages and pushing the choanae further backward. The possession of small posterior palatine foramina shows a closer connection with Amphichelydian stock than exists in the Cheloniidae, which have lost these foramina. Williston thinks that the cervical vertebra; indicate pleurodiran characters. The posses- sion ot strongly developt transverse processes is to be regarded as an inheritance rather from the Amphichelydia than from the Pleurodira. The articular ends of the cervical vertebras show decided affinities with the Cryptodira. An intervertebral articulation which is 26 mm. wide and onh 15 mm. high, belonging to a centrum only 26 mm. long, would not lend itself readily to flexure sidewise, while it would permit easy flexure in a perpendicular plane. 1 he Desmatochelyidae are to be arranged close to the Cheloniidae; but their many prim- itive characters demand that they be kept in a distinct family, tor those who are seeking a Cretaceous ancestor for the modern sea-turtles, Desmatochelys presents itself as a more eligible form than any of the Cretaceous Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble th
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