Apr. 1903. North American Plesiosaurs — Williston. 57 



BRACHAUCHENIUS LUCASI, GEN. ET SP. NOV. 



The specimen upon which this genus and species are based is 

 one of much interest, not only because of its excellent preservation 

 and preparation, but also because of the new features which it 

 presents. It consists of the skull, neck, and larger part of the dorsal 

 column, all lying together in their natural relationships, and all with 

 the ventral surface exposed, in the prepared specimen. The specimen 

 was collected some years ago near Delphos, in Ottawa County, Kan- 

 sas. Its horizon is the Benton Cretaceous. It is now preserved in a 

 wall-case in the National Museum. I desire to express my hearty 

 thanks to the authorities of the National Museum for permission to 

 study and describe the specimen, and especially to Mr. F. A. Lucas 

 for much kind assistance. It gives me great pleasure to honor, in 

 the specific name, one who has done much valuable work in American 

 paleontology. (Pis. XXIV, XXV.) 



Skull. — The palatal surface of the skull lies exposed, with the 

 mandibles in position. There has been but little distortion or dis- 

 placement, the mandibles being slightly depressed and pushed to the 

 left. The limestone matrix 'has been carefully removed from most 

 parts, leaving the bones entirely clean. The sutures are entirely 

 clear, and there are but few adventitious fractures to obscure the 

 relations of the parts. It is certain that additional excavation will 

 reveal further characters of importance, but not many, unless the 

 specimen be entirely removed from the matrix. The specimen as 

 now mounted in the wall slab makes a very interesting and instructive 

 display, but I believe that some day it will be advisable to remove it 

 entirely from its limestone bed and mount it after the manner of a 

 recent skeleton. It was fortunate, however, that this was not done 

 before a careful examination had been made of the natural relations 

 of the bones, as it would have been difficult to believe that the neck 

 comprised but thirteen vertebrae, had not the matrix conclusively 

 demonstrated the fact. It is the shortest-necked plesiosaur known, 

 differing in this respect not greatly from the short-necked aquatic 

 saurians of other orders. 



The pterygoids extend far back to unite with the lower end <>t the 

 quadrates, apparently quite as usual in the plesiosaurs, though tin- 

 precise place of junction is obscured by the mandibles ; the process 



