Page:North American Plesiosaurs- Elasmosaurus, Cimoliasaurus, and Polycotylus.pdf/8

228 some of the vertebræ wrongly. The first dorsal vertebra, as he describes it, is in reality a posterior cervical, while his seventh is either the last pectoral or the first true dorsal. From his description, I make out sixty-two as the number of cervical vertebrae preserved, and eighteen dorsals. As this number of dorsals is smaller than is known in any other species of plesiosaurs, I am confident that the series was not complete. If Cope was correct in the serial relations of the cervical vertebræ described, the species is quite distinct from anything otherwise described. His descriptions of the

and pelvic girdles and of the limbs indicate an excellent specimen now in the, which will be shortly described by Mr. E. S. Riggs, and a perfect from the Hailey shales in the collection of the University of Chicago.

 Williston. Niobrara Cretaceous of Kansas.

This species, based upon an excellent skull and a connected series of eighteen cervical vertebrae in the museum of the University of Kansas, I identify with much certainty in an