78 MEMOIRS OF THE CARNEGIE MUSEUM 
The present paper is based upon the remains of three individuals, Nos.* 603, 878 
and 919, from as many widely separated localities. All have been entirely freed 
from the matrix or worked out in relief by the writer and because of their remark- 
ably well preserved condition several important osteological characters are shown 
for the first time. 
In studying this material it was found necessary to compare it with the types of 
Baptanodon, preserved in the Yale Museum collections. Through the kindness of 
the late Dr. C. E. Beecher the author was permitted to study not only the types 
(B. natans and B. discus), but all of the Ichthyosaurian remains contained in the 
collections of that museum, comprising parts of some nine or ten individuals. At 
the American Museum of Natural History through the courtesy of Dr. W. D. 
Matthew I was given the privilege of examining the quite complete Jurassic Ichthyo- 
saurian skeleton in that collection. Through my former instructor, the late Dr. W. 
C. Knight, I was accorded the privilege of studying the material at the Wyoming 
University, Laramie, Wyoming, part of which I helped collect. Thus practically all 
of the important Ichthyosaurian remains known from the Jurassic of North America 
have been personally examined during the preparation of this paper. 
My acknowledgments are especially due the late Mr. J. B. Hatcher for the 
encouragement and kind consideration shown me in all matters pertaining to the 
preparation of this study. 
For the preparation of the drawings used the author is grateful to the skill and 
patience of Mr. Sidney Prentice. 
The photographs are by Mr. A. 8. Coggeshall. 
OccURRENCE AND DiIstrIBUTION. 
The Ichthyosaurian remains collected from the Jurassic of America have all 
been found in the upper part of the marine division of that formation. ‘This marine 
strata was designated by Marsh as the Baptanodon Beds,‘ and included all of the 
Jurassic lying between the freshwater or Atlantosawrus Beds above and the red beds 
or Triassic (?) below. The Hallopus Beds of Marsh, if at all recognizable, have never 
been found in contact with the marine beds and their exact position in relation to 
these beds is yet undetermined. 
Knight® has proposed the name Shirley for the marine series without assigning 
any place or giving any reasons for supplanting the old and generally accepted 
term Baptanodon Beds, which has priority. 
5 The numbers refer to the Card Catalogue of Fossil Vertebrates in the Collection of the Carnegie Museum. 
‘Marsh, O. C., “‘ The Reptilia of the Baptanodon Beds,’’ Amer. Jour. of Sci. (3), Vol. 50, pp. 405-406, 1895. 
5Knight, W. C., Jurassic Rocks of Southeastern Wyoming,’’ Bull. of the Geol. Soc. of America, Vol. XI., pp. 377- 
388, May, 1900. 
