‘ 
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. (Pls. XXIV, XXV.) 
Sxutt.—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 hmestone 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 fpterygotds extend far back to unite with the lower end of the 
quadrates, apparently quite as usual in the plesiosaurs, though the 
precise place of junction is obscured by the mandibles; the process 
