378 W. 0. Knight— Jurassic Vertebrates from Wyoming. 



Art. XINII.—Some new Jurassic Vertebrates from Wyom- 

 ing. Second Paper by Wilbur C. Knight. 



The University of Wyoming has in its collection of Jurassic 

 vertebrates partial remains of four swimming saurians, that in 

 a general way resemble plesiosaurs. The discovery of these 

 remains is of considerable value to American Mesozoic geolo- 

 gists, for these data will be very valuable in correlating the 

 American and European Jurassic. It is of equal importance in 

 separating the term Jura-Trias, and making American Jurassic 

 and Triassic terranes, in the place of the consolidated term 

 that has been in use since the early surveys in the Rocky 

 Mountains. The largest of these four species surpasses in size 

 the European Pliosaur, and owing to the many peculiar char- 

 acters it has been deemed necessary to create a new genus. 



Megalneusaurus gen. nov. 



Vertebra over two-thirds as long as wide ; height of the 

 centra nearly equalling the transverse diameter. Anterior cer- 

 vical vertebra deeply cupped anteriorly and slightly concave 

 posteriorly; neural arches united by suture and always found 

 detached. Dorsal vertebra cylindrical with a forward over- 

 hanging of the upper part of the centra ; anterior faces slightly 

 concave, posterior flat ; both faces with mammilla ; zyga- 

 pophyses spoon-shaped ; neural arches firmly sutured to centra ; 

 neural spines low and nearly as long as the centra. Caudle 

 vertebra with slightly concave faces and mammilla. Cora- 

 coids produced in front of the glenoid cavity. Joints of the 

 digits alternate with each other. Phalanges concave proxi- 

 mally, convex distally. Ulna and radius short, broad, heavy 

 bones, nearly equal in size, and separated by a small central 

 opening. Below this opening the two bones are united by 

 rugose surfaces ; above they are united by a horn-like projec- 

 tion extending from the ulna and fitting into a depression in 

 the radius. Ulna concave proximally and convex distally. 

 Padius, inner one-fourth of the proximal end concave ; outer 

 three-fourths convex. Carpal bones six in number and all 

 angular. Humerus a powerful bone with a prismatic shaft ; 

 distally broad and flat ; proximally expanded into a spherical 

 head. The anterior side of the head of humerus with a 

 groove ; the posterior side with a broad shallow indentation. 

 This genus in many respects resembles Pliosaurus, but it also 

 has characters that are common to Peloneustes and Plesio- 

 saurus. It represents the largest known animals of the order 

 Sauropterygia. 



