Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/104

 98 THE EXTINCT BATRACHIA, REPTILIA The figure 29 is the result of the preceding considerations, but it is not to be consid-ered as completely demonstrated. They go to show the narrow and prominent form of the abdominal region, which. was associated with its' posterior position, and the great lengths ofethe femora. Fig. a is a front view of the pubis; b is an internal view of the ischium of Clepsysaurus. Dentition.--'The teeth of this genus are very much smaller in relation to the size of the animal than in Iguanodon. They bear enamel on one stud-tee only, the external for the inferior series as Leidy points out. Thus but one edge of the worn crowns is enam-elled, and acts functionally like that of the anterior faces of the incisors of Rodents: They produce shear-like edges, cutting the vegetable food by a horizontal transverse motion. IIADROSAUTIUS MIRADIL1S, Leidy. Proceed. A. N. Sci., Phil., 186$. 199. Truthodon 'Wrath's, Trans. Am. Phil. Soc., XI, 1860, 140. Tab. Upper Jurassic Bad Lands of Judith River, Nebraska. Known from teeth, and perhaps vertebrte and phalanges. ILADROSAURITS FOULKII, Leidy. Proc. Acad. Nat. Sei., Phil., 1838, 218, Cret. Rept. U. S. 76, Tab. XII to XVII. Cretaceous green sand, New Jersey. There are eight localities in the green sand of Cretaceous age in New Jersey, from which I have seen portions of this species. HADIIOSAURITS ?OCCIDENTAL'S, Leidy. hespesius oceidentalis. Trans. Amer. Philos°. Soc., XI., 1860, 151, tab. ?Cretaceous Beds of Nebraska, between Moreau and Grand Rivers. Of this supposed species, Leidy says, "had the remains of Thespesius and Truchodom been found in a deposit of the same age, I should have unhesitatingly referred them to the same animal, and I cannot avoid the suspicion that future investigation may determine them to be the same.'' In this be refers to Hadrosaurus mirabilis, which Hayden discovered in the Jurassic of Judith River, while the types of Thespesius were found by the same geologist, in a bed with other vertebrates, mostly reptiles, which he determined to be of Miocene age. Now, the extreme improbability of this type occurring in a Miocene bed will occur to many palaeontologists, as has to me. With the view of determining this point if possible, I instituted an examination of the forms brought by Dr. Hayden from this locality, and first of that most characteristic animal, the Isehyrutherium, of Leidy. This, as has appeared in the preceding pages, I believe to be a reptile, allied to Plesiosaurus, a, conclusion which at once estab-lishes the Mesozie age of the bed. It coincides with the presence of Hadrosaurus, in indicating Cretaceous or upper Jurassic age.