1883.] NATURAL SCIENCES OF PHILADELPHIA. 107 



it may have scraped leaves from the ends of branches, but the 

 appearances indicate softer and less tenacious food. Could we 

 suppose that the waters of the great Laramie lakes had supplied 

 abundant aquatic plants without woody tissue, we would have the 

 condition appropriate to this curious structure. Nymphseas, 

 Nuphars, Potamogetons, Anacha?-is, MyriophyUum and similar 

 growths could have been easily gathered by this double-spoon- 

 like bill, and have been tossed, b}' bird-like jerks of the head 

 and neck, back to the mill of small and delicate teeth. In 

 order to submit the food to the action of these vertical shears, the 

 jaws must have been opened widely enough to permit their edges 

 to clear each other, and a good deal of wide gaping must, there- 

 fore, have accompanied the act of mastication. This would be 

 easy, as the mouth opens, as in reptiles and birds generally, to a 

 point behind the line of the position of the eye. The eye was 

 evidently of large size. On the other hand the indications are 

 that the external ear was of very small size. There is a large 

 tract that might have been devoted to the sense of smell, but 

 whether it was so or not is not easily ascertained. 



We can suppose that the huge hind-legs of this genus and of 

 Hadrosaurus were especially useful in wading in the water that 

 produced their food. When the bottom was not too soft, they 

 could wade to a depth of ten or more feet, and, if necessary, 

 drag aquatic plants from their hold below. Fishes might have 

 been available as food when not too large, and not covered with 

 bony scales. Most of the fishes of the Laramie period, are, how- 

 ever, of the latter kind (genus Clastes). The occurrence of several 

 beds of lignite in the foj-mation shows that vegetation was 

 abundant. 



EXPLANATION OF PLATES. 



(All the figures are one-seventh of the natural size.) 



Plate IV. Side view of skull of Diclonius mirabilis. 

 Plate V. The same viewed from above. 

 Plate VI. Inferior view of the same. 



Plate VII. Fig. 1, View of occipital region of the same. Fig. 2, View of 

 the extremity of the muzzle from the front. 



The complete iconography of this species will appear in the third volume 

 of the Report of the United States Geological Survey of the Territories, 

 under F. V. Hayden and J. W. Powell, now in course of preparation. 



