Apr. 1903. North American Plesiosaurs — Willi STON. 11 



Wyoming. The processes are attached. The description will apply 

 to caudal vertebrae of various genera. 



URONAUTES. 

 Cope, Proc. Acad. Nat. Sci. Phil. 1876, 345. 

 cetiformis Cope, 1. c. 346. — Fort Pierre (?) Cretaceous, Montana. 



species Cope, Amer. Nat. 1887, 566. — Fox Hills Cretaceous, New 

 Mexico. 



This genus was based upon cervical, dorsal and caudal vertebrae. 

 The cervicals are short, with the processes partly attached, and the 

 ribs single-headed. 



Professor Cope referred the type species to the Fox Hills Cre- 

 taceous with doubt. I suspect, rather, that the horizon is Fort 

 Pierre. 



OROPHOSAURUS. 



Cope, Amer. Naturalist, 1887, 564. 



PAUCIPORUS Cope, 1. c. — Fox Hills Cretaceous of New Mexico. 



Based upon parts of three cervical vertebrae. The neural arches 

 art coossified, the ribs free. Centra short; ribs single-headed. 



P1PTOMERUS. 

 Cope, Amer. Nat. 1867, 564. 

 UEGALOPORUS Cope, 1. c. 564. — Fox Hills Cretaceous, N» \v Mexico. 

 MICROPORUS Cope, 1. c. — Fox Hills Cretaceous, New Mexico. 

 HEXAGONUS Cope. 1. c. — Fox Hills Cretaceous, New Mexico. 



This genus and species are based upon cervical and dorsal verte- 

 bra only. The cervicals are short, the processes free and the ribs 

 single-headed. 



TR1NACROMERUM. 

 < Cragin, Amer. Geologist, Dec. 1888. 



• i'.kn iomantm Cragin, 1. c. ; ibid, 1891, 171. — Penton Cretaceous, 

 Kansas. 



A large part of the skeleton was known to the describer, includ- 

 ing the skull, vertebra-, part of the girdles and limbs. 



