o) 
(S 
MEMOIRS OF THE CARNEGIE MUSEUM 
Two fishes have been referred to by Knight as probably coming from these beds. 
Amiopsis dartom, Eastman. Pholidophorus americanus, Eastman. 
Hatcher ® gives the geographical extent of these beds as follows: ‘The marine 
Baptanodon Beds throughout Wyoming and South Dakota are everywhere found 
accompanying and underlying the freshwater Atlantosawrus Beds though thinning 
out toward the south and entirely disappearing as we approach the Wyoming and 
Colorado state line.” He has also shown that the lowermost 150 feet of the Jura 
at Cafion City, Colorado, may be the freshwater equivalents of the marine Bap- 
tanodon Beds farther north. 
By far the largest number of skeletons of Baptanodon now known have been col- 
lected from the exposures of southeastern Wyoming, though several individuals 
have been discovered in the strata farther north. There is one specimen (No. 919) 
in the collections of this museum from the marine beds of north central Wyoming. 
Their remains are also reported from South Dakota. 
Of the dozen or more specimens I have collected or helped collect every one was 
found more or less enclosed in one of those concretionary masses spoken of by 
Knight, the form and size of these concretions being dependent upon the shape 
and position of the skeleton enclosed. When exposed to the atmosphere, as often 
happens by the carrying away of the surrounding shale or clay, the concretion in- 
variably cracks into an innumerable number of pieces. 
It has been my experience that the anterior portion of the snout, the end of the 
tail and tips of the extremities are not enclosed by the concretion, and when present 
are found in the soil surrounding the rock. This will account for the poorly pre- 
served condition of these parts in the material under discussion. Of the six skulls 
and parts of skulls examined the tip of the beak is wanting in every instance, and 
peculiar as it may seem, the anterior fourth of each protruded from the concretion 
into the surrounding shale. The quite complete posterior caudal series preserved 
in the collection of the University of Wyoming came from the clay. Four paddles 
have been studied and although the bones of the proximal segments are retained 
in their relative positions in the matrix, the distal part is wanting in every instance. 
In one example, the type of B. discus (No. 1955)," quite a number of the smaller or 
distal disks were preserved but their color and state of preservation indicated that 
they had come from the soft clay surrounding the concretion which contained-the 
skeleton proper. 
Lit. cit., p. 70. 
0 Catalogue number of the Yale Myseum. 
