This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...diameter of the dorsal centra is less than onehalf of their height. The single fragmentary specimen of C. piscosus represents a form smaller than the average of C. petrinus. The vertebral centra are relatively longer, their anteroposterior diameter equaling more than half of the height. The anterior and posterior faces of the centra are sharply and regularly concave from the periphery to the center of the face. C. grandis was founded on a fragment of a caudal vertebra from the West Humboldt Range, and possibly represents a large individual of C. petrinus. Fragmentary material recently obtained at New Pass, Nevada, is referred to a new species, C. nevadanus. Tt is distinguished mainly by the short and massive elements of the epipodial region of the hind limb. CYMBOSPONDYLUS PETRINUS Leidy. Cymbospondylus petrinus Leidy, Proc. Philad. Acad. Sc., 1868, vol. 20. p. 178. Chonespondylus grandis Leidy, Ibid. Cynibospondylus petrinus (Merriam), Univ. Calif. Publ., vol. 3, p. 106. Cynibospondylusf grandis (Merriam), Ibid. This species is the best known of the American Triassic ichthyosaurs, being represented by many individuals, which collectively exhibit the greater part of the skeletal structure. It occurs in the exposures of Middle Triassic limestones in the West Humboldt Range of Nevada. Closely allied to the typical C. petrinus is a form. C. nevadanus, which has been obtained in Middle Triassic limestones exposed at New Pass, twenty-eight miles west of Austin, Nevada. C. petrinus is represented by individuals averaging over twenty feet in length. In one very large skull, no. 9954, which does not seem to be specifically separable from this form, the dimensions of corresponding parts are about 50 per cent. larger than in specimen 9950 of C. petrinus, in which the...