Page:North American Plesiosaurs- Elasmosaurus, Cimoliasaurus, and Polycotylus.pdf/7

Rh in different species of Polycotylus and , both relatively short-necked and long-headed plesiosaurs. Much doubt and even ridicule have been thrown upon this supposed habit and the use of the pebbles by these reptiles. But the cumulative testimony of writers, both on this and the other side of the Atlantic, is quite conclusive. It has been assumed that the plesiosaurs could not have utilized the pebbles as a means of digestion in a muscular stomach. Dr. Eastman, who has vigorously opposed the idea of the possession of such a -like structure on the part of the plesiosaurs, seems to have been quite unaware of the fact that the modern crocodiles have a real, bird-like and muscular gizzard, and so described by Dr. Gadow. The crocodiles have a similar habit, or at least such a habit has been imputed to them, and it is not at all unreasonable to suppose that, strange as it may seem, the plesiosaurs had a real, muscular bird-like, which utilized the pebbles in whatever way the crocodiles may utilize them.

 Cope. Cretaceous of New Jersey.

This species was based upon two mutilated and isolated cervical centra from New Jersey. It seems far more probable that these vertebræ really belong with Cimoliasaurus. Cope afterwards associated with this species an excellent series of vertebræ from the Pierre, which I have studied in the American Museum. I have not the least doubt but that Cope was in error in this collocation. I am not sure of the distinction of this specimen from E. platyurus, though a careful comparison of the measurements and sketches made by myself will, I think, decide their identity. If not E. platyurus, the species is doubtless entitled to a new specific name.

 Cope. Fort Pierre Cretaceous of Montana.

This species was based upon nineteen centra without processes, and all more or less mutilated; now in the museum of the Academy of Natural Sciences at Philadelphia. I can not distinguish them specifically from E. platyurus.

 Cope. Niobrara Cretaceous.

This species was based upon much better material than was either of the foregoing ones, and it is both recognizable and distinct. Unfortunately, no figures have ever been given of the type specimen, and I have not had, so far, an opportunity to study the specimen. As in his other descriptions, Cope